Multiheight contact via structures for a multilevel interconnect structure

ABSTRACT

Contact openings extending to sacrificial layers located at different depths can be formed by sequentially exposing a greater number of openings in a mask layer by iterative alternation of trimming of a slimming layer over the mask layer and an anisotropic etch that recesses pre-existing contact openings by one level. In one embodiment, pairs of an electrically conductive via contact and electrically conductive electrodes can be simultaneously formed as integrated line and via structures. In another embodiment, encapsulated unfilled cavities can be formed in the contact openings by non-conformal deposition of a material layer, electrically conductive electrodes can be formed by replacement of portions of the sacrificial layers, and the electrically conductive via contacts can be subsequently formed on the electrically conductive electrodes. Electrically conductive via contacts extending to electrically conductive electrodes located at different level can be provided with self-aligned insulating liner.

RELATED APPLICATION

This application is related to U.S. application Ser. No. 14/468,644, theentire contents of which are incorporated by reference herein.

FIELD

The present disclosure relates generally to the field of metalinterconnect structures, and specifically to multilevel metalinterconnect structures including electrically conductive via contactshaving different heights, and methods of manufacturing the same.

BACKGROUND

Multilevel metal interconnect structures are routinely employed toprovide electrical wiring for a high density circuitry, such assemiconductor devices on a substrate. Continuous scaling ofsemiconductor devices leads to a higher wiring density as well as anincrease in the number of wiring levels. Recently, ultra high densitystorage devices have been proposed using a three-dimensional (3D)stacked memory structure sometimes referred to as a Bit Cost Scalable(BiCS) architecture. Such ultra high density storage devices include alarge number of interconnect wiring levels. For example, a 3D NANDstacked memory device may include at least as many number of wiringlevels as the total number of control gate electrodes employed for the3D NAND stacked memory device.

Various schemes for constructing electrically conductive via contactsextending to different electrically conductive electrodes located atdifferent wiring levels of memory devices have been proposed in the art.For example, U.S. Pat. No. 8,394,716 to Hwang et al. and U.S. PatentApplication Publication No. 2009/0230449 to Sakaguchi et al. teachformation of conductive via structures extending from a same top surfaceto top surfaces of electrically conductive electrodes located atdifferent levels by staggering end portions of the electricallyconductive electrodes. Specifically, end portions of electricallyconductive electrodes are staggered such that an edge of each overlyingelectrically conductive electrode is laterally offset inward from anedge of any underlying electrically conductive electrodes throughout theentirety of a stack of the electrically conductive electrodes.

SUMMARY

According to an aspect of the present disclosure, a method of makingmulti-level contacts is provided. An in-process multilevel device isprovided, which comprises a device region and a contact region includinga stack of plurality of alternating sacrificial layers and insulatinglayers located over a major surface of a substrate. A plurality ofcontact openings is formed, each of which extends substantiallyperpendicular to the major surface of the substrate to the plurality ofsacrificial layers. Each of the plurality of contact openings extendsthrough the stack to a respective one of the sacrificial layers. Thesacrificial layer are selectively removed from the stack to form aplurality of recesses extending substantially parallel to the majorsurface of the substrate between the insulating layers. A plurality ofelectrically conductive via contacts is deposited in the plurality ofthe contact openings and a plurality of electrically conductiveelectrodes in the plurality of recesses in one deposition step.

According to another aspect of the present disclosure, a method ofmaking contact openings in a stack of layers is provided. A stack ofplurality of alternating sacrificial layers and insulating layers isformed over a major surface of a substrate. A mask with a plurality ofopenings is formed over the stack. A slimming layer is formed over themask. The slimming layer is etched to reduce its thickness and width toexpose a first opening in the mask. A portion of a first insulatinglayer exposed in the first opening is etched to form a portion of afirst contact opening in the first insulating layer extending to a firstsacrificial layer located under the first insulating layer in the stack.The slimming layer is etched to reduce its thickness and width to exposea second opening in the mask. A portion of the first insulating layerexposed in the second opening is etched to form a portion of a secondcontact opening in the first insulating layer extending to the firstsacrificial layer. A portion of the first sacrificial layer and aportion of a second insulating layer are etched through the firstcontact opening to extend the first contact opening to a secondsacrificial layer located under the second insulating layer in thestack. An insulating liner is formed on a sidewall of the first and thesecond contact openings.

According to yet another aspect of the present disclosure, athree-dimensional NAND device is provided, which includes a substratehaving a major surface, and a stack of plurality of alternating wordlines and insulating layers located over the major surface of thesubstrate and extending substantially parallel to the major surface ofthe substrate. The plurality of word lines comprise at least a firstword line located in a first device level and a second word line locatedin a second device level located over the major surface of the substrateand below the first device level. The three-dimensional NAND devicefurther includes a semiconductor channel. At least one end portion ofthe semiconductor channel extends substantially perpendicular to themajor surface of the substrate through the stack. The three-dimensionalNAND device further includes at least one charge storage region locatedadjacent to the semiconductor channel, and a plurality of electricallyconductive via contacts extending substantially perpendicular to themajor surface of the substrate. Each of the plurality of electricallyconductive via contacts extends through the stack to contact an uppersurface of a respective one of the plurality of word lines. Aninsulating liner is located around each of the plurality of electricallyconductive via contacts. The insulating liner isolates each electricallyconductive via contact from all the word lines in the stack except arespective one of the plurality of word lines whose upper surface iscontacted by the respective electrically conductive via contact.

According to still another aspect of the present disclosure, a method offorming contacts in a multilayer memory device is provided. Anin-process memory device is provided, which includes a contact region, adevice region, and a stack of alternating plurality of sacrificiallayers and insulating layers over a substrate and extending in a firstdirection substantially parallel to a major surface of the substratefrom the contact region to the device region. A hard mask layer isformed over the contact region and the device region. A plurality ofcontact openings is formed in the contact region. Each contact openingextends in a second direction substantially perpendicular to the majorsurface of the substrate through the hard mask layer and a portion ofthe stack to a respective sacrificial layer. An insulating liner isformed, which covers sidewalls of each contact opening of the pluralityof contact openings. The insulating liner does not cover a bottom ofeach contact opening such that a portion of the respective sacrificiallayer is exposed at the bottom of the contact opening. A non-conformallayer is formed over the hard mask layer. The non-conformal layer coversa top opening of each contact opening to form a corresponding contactopening air gap.

According to even another aspect of the present disclosure, anin-process memory device is provided, which includes a contact region, adevice region, and a stack of alternating plurality of sacrificiallayers and recesses over a substrate and extending in a first directionsubstantially parallel to a major surface of the substrate from thecontact region to the device region. The in-process memory devicefurther includes a hard mask layer formed over the contact region andthe device region; a plurality of contact openings in the contactregion, each contact opening extending in a second directionsubstantially perpendicular to the major surface of the substratethrough the hard mask layer and a portion of the stack to a respectivesacrificial layer; an insulating liner covering sidewalls of eachcontact opening of the plurality of contact openings, wherein theinsulating liner does not cover a bottom of each contact opening suchthat a portion of the respective sacrificial layer is exposed at thebottom of the contact opening; and a non-conformal layer over the hardmask layer that covers a top opening of each contact opening to form acorresponding contact opening air gap. Each one of the plurality ofrecesses contacts a respective contact opening air gap.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-15 illustrate sequential vertical cross-sectional views of afirst exemplary structure employed to fabricate a device structurecontaining vertical NAND memory devices at corresponding processingsteps according to a first embodiment of the present disclosure.

FIGS. 2, 4, 5, 6, and 8 show bird's eye view of cut-out portions of thefirst exemplary structures.

FIG. 14 includes an inset showing a magnified view of a portion of thefirst exemplary structure.

FIGS. 16-26 illustrate sequential vertical cross-sectional views of asecond exemplary structure employed to fabricate a device structurecontaining vertical NAND memory devices according to a second embodimentof the present disclosure.

DETAILED DESCRIPTION

As discussed above, the present disclosure is directed to multilevelmetal interconnect structures including electrically conductive viacontacts having different heights, and methods of manufacturing thesame, the various aspects of which are described below. The embodimentsof the disclosure can be employed to form various structures including amultilevel metal interconnect structure, a non-limiting example of whichincludes semiconductor devices such as three-dimensional monolithicmemory array devices comprising a plurality of NAND memory strings. Thedrawings are not drawn to scale. Multiple instances of an element may beduplicated where a single instance of the element is illustrated, unlessabsence of duplication of elements is expressly described or clearlyindicated otherwise. Ordinals such as “first,” “second,” and “third” areemployed merely to identify similar elements, and different ordinals maybe employed across the specification and the claims of the instantdisclosure. As used herein, a first element located “on” a secondelement can be located on the exterior side of a surface of the secondelement or on the interior side of the second element.

A monolithic three dimensional memory array is one in which multiplememory levels are formed above a single substrate, such as asemiconductor wafer, with no intervening substrates. The term“monolithic” means that layers of each level of the array are directlydeposited on the layers of each underlying level of the array. Incontrast, two dimensional arrays may be formed separately and thenpackaged together to form a non-monolithic memory device. For example,non-monolithic stacked memories have been constructed by forming memorylevels on separate substrates and vertically stacking the memory levels,as described in U.S. Pat. No. 5,915,167 titled “Three DimensionalStructure Memory.” The substrates may be thinned or removed from thememory levels before bonding, but as the memory levels are initiallyformed over separate substrates, such memories are not true monolithicthree dimensional memory arrays. The various three dimensional memorydevices of the present disclosure include a monolithic three-dimensionalNAND string memory device, and can be fabricated employing the variousembodiments described herein.

The present inventors realized that the methods of Huang and Sakaguchirequire lateral discontinuity of many electrically conductive electrodesat least along one direction within regions of the electricallyconductive via contacts. Further, the methods of Huang and Sakaguchiprevent extension of any electrically conductive via contact through anarea of a pre-existing electrically conductive electrode, therebyplacing a significant limitation on the design and the density of thevarious components in a metal interconnect structure. At least someembodiments of the present disclosure provide methods for forming a highdensity multilevel metal interconnect structure without significantrestrictions on the design of various metal interconnect componentsand/or with minimal processing complexity and cost.

According to various embodiments of the present disclosure, contactopenings extending to sacrificial layers located at different depths canbe formed by sequentially exposing a greater number of openings in amask layer by iterative alternation of trimming of a slimming layer overthe mask layer and an anisotropic etch that recesses pre-existingcontact openings by one level. In one embodiment, pairs of anelectrically conductive via contact and an electrically conductiveelectrodes can be simultaneously formed as integrated line and viastructures. In another embodiment, encapsulated unfilled cavities can beformed in the contact openings by non-conformal deposition of a materiallayer, electrically conductive electrodes can be formed by replacementof portions of the sacrificial layers, and the electrically conductivevia contacts can be subsequently formed on the electrically conductiveelectrodes. A metal interconnect structure can be provided in whichelectrically conductive via contacts extending to electricallyconductive electrodes located at different levels are provided withself-aligned insulating liner to provide electrical isolation from allother electrically conductive electrodes except one to which arespective electrically conductive via contact is electrically shorted.

Referring to FIG. 1, a first exemplary structure is illustrated, whichcan be employed, for example, to fabricate a device structure containingvertical NAND memory devices according to a first embodiment of thepresent disclosure. The first exemplary structure includes a substrate8, which can be a semiconductor substrate. Various semiconductor devicescan be formed on, or over, the substrate 8 employing methods known inthe art. For example, an array of memory devices can be formed in adevice region 100, and at least one peripheral device 20 can be formedin a peripheral device region 200. Electrically conductive via contactsto the electrically conductive electrodes of the devices in the deviceregion 100 can be subsequently formed in a contact region 300.

The substrate 8 can include a substrate semiconductor layer 10. Thesubstrate semiconductor layer 10 is a semiconductor material layer, andcan include at least one elemental semiconductor material, at least oneIII-V compound semiconductor material, at least one II-VI compoundsemiconductor material, at least one organic semiconductor material, orother semiconductor materials known in the art. The substrate 8 has amajor surface 9, which can be, for example, a topmost surface of thesubstrate semiconductor layer 10. The major surface 9 can be asemiconductor surface. In one embodiment, the major surface 9 can be asingle crystalline semiconductor surface.

As used herein, a “semiconductor material” refers to a material havingelectrical conductivity in the range from 1.0×10⁻⁵ Ohm-cm to 1.0×10⁵Ohm-cm, and is capable of producing a doped material having electricalconductivity in a range from 1 Ohm-cm to 1.0×10⁵ Ohm-cm upon suitabledoping with an electrical dopant. As used herein, an “electrical dopant”refers to a p-type dopant that adds a hole to a balance band within aband structure, or an n-type dopant that adds an electron to aconduction band within a band structure. As used herein, a “conductivematerial” refers to a material having electrical conductivity greaterthan 1.0 Ohm-cm. As used herein, an “insulator material” or a“dielectric material” refers to a material having electricalconductivity less than 1.0×10⁻⁵ Ohm-cm. All measurements for electricalconductivities are made at the standard condition.

Optionally, at least one doped well 14 can be formed within thesubstrate semiconductor layer 10 such as a single crystalline siliconsurface.

Optionally, select gate electrodes (not shown) can be formed within, oron top of, the substrate semiconductor layer 10 using any suitablemethods for implementing the array of vertical NAND strings. Forexample, a lower select gate device level may be fabricated as describedin U.S. patent application Ser. No. 14/133,979, filed on Dec. 19, 2013,U.S. patent application Ser. No. 14/225,116, filed on Mar. 25, 2014,and/or U.S. patent application Ser. No. 14/225,176, filed on Mar. 25,2014, all of which are incorporated herein by reference. While thepresent disclosure is described employing an embodiment in which asource region 12 is formed in a region laterally offset from a verticalportion of each channel and memory structure 55, and a horizontalportion of the substrate semiconductor layer 10 or the at least onedoped well 14 that contacts the vertical portion of the channel andmemory structure 55 can function as a horizontal portion of the channel,embodiments are expressly contemplated herein in which a first electrodeor source region 12 is formed directly underneath channel and memorystructures 55 of memory cells, as described in U.S. patent applicationSer. No. 14/317,274, filed on Jun. 27, 2014, which is incorporatedherein by reference. A select transistor can be formed between the topof the substrate semiconductor layer 10 and the bottommost control gateof the memory devices.

At least one shallow trench isolation structure 16 and/or at least onedeep trench isolation structure (not shown) may be employed to provideelectrical isolation among various semiconductor devices on thesubstrate 8. The at least one peripheral device 20 formed in theperipheral device region 200 can include any device known in the art andneeded to support the operation of the semiconductor devices in thedevice region 100. The at least one peripheral device 20 can include adriver circuit associated with the array of the memory devices in thedevice region 100. The at least one peripheral device can comprisetransistor device in the driver circuit. In one embodiment, the at leastone peripheral device can include one or more field effect transistors,each of which can include a source region 201, a drain region 202, abody region 203 (e.g., a channel region), a gate stack 205, and a gatespacer 206. The gate stack 205 can include any type of gate stack knownin the art. For example, each gate stack 205 can include, from one sideto another, a gate dielectric, a gate electrode, and an optional gatecap dielectric. Optionally, a planarization dielectric layer 208including a dielectric material may be employed in the peripheral deviceregion 200 to facilitate planarization of the portion of material stacksto be subsequently formed on the substrate 8.

A stack of alternating layers of a first material and a second materialdifferent from the first material is formed over a top surface of thesubstrate 8. The top surface of the substrate 8 can include the topsurface of a first electrode 12 and/or a surface of a body region of afield effect transistor. In one embodiment, the stack can include analternating plurality of insulator layers 32 and sacrificial layers 42.As used herein, an “an alternating plurality” of first elements andsecond elements refers to a structure in which an instance of the firstelements and an instance of the second elements form a unit that isrepeated within a stacked structure. The first elements may have thesame thickness thereamongst, or may have different thicknesses. Thesecond elements may have the same thickness thereamongst, or may havedifferent thicknesses.

The stack of the alternating layers is herein referred to as analternating stack (32, 34). In one embodiment, the alternating stack(32, 42) can include insulator layers 32 composed of the first material,and sacrificial layers 42 composed of a second material different fromthat of insulator layers 32. The sacrificial layers 42 may comprise anelectrically insulating material, a semiconductor material, or aconductive material. The second material of the sacrificial layers 42can be subsequently replaced with electrically conductive electrodeswhich can function, for example, as control gate electrodes of avertical NAND device.

The first material of the insulator layers 32 can be at least oneelectrically insulating material. As such, each insulator layer 32 canbe an insulating material layer. Electrically insulating materials thatcan be employed for the insulator layers 32 include, but are not limitedto silicon oxide (including doped or undoped silicate glass), siliconnitride, silicon oxynitride, organosilicate glass (OSG), spin-ondielectric materials, dielectric metal oxides that are commonly known ashigh dielectric constant (high-k) dielectric oxides (e.g., aluminumoxide, hafnium oxide, etc.) and silicates thereof, dielectric metaloxynitrides and silicates thereof, and organic insulating materials.

The second material of the sacrificial layers 42 is a sacrificialmaterial that can be removed selective to the first material of theinsulator layers 32. As used herein, a removal of a first material is“selective to” a second material if the removal process removes thefirst material at a rate that is at least twice the rate of removal ofthe second material. The ratio of the rate of removal of the firstmaterial to the rate of removal of the second material is hereinreferred to as a “selectivity” of the removal process for the firstmaterial with respect to the second material. Non-limiting examples ofthe second material include silicon nitride, an amorphous semiconductormaterial (such as amorphous silicon), and a polycrystallinesemiconductor material (such as polysilicon).

In one embodiment, the insulator layers 32 can include silicon oxide,and sacrificial layers can include silicon nitride sacrificial layers.The first material of the insulator layers 32 can be deposited, forexample, by chemical vapor deposition (CVD). For example, if siliconoxide is employed for the insulator layers 32, tetraethyl orthosilicate(TEOS) can be employed as the precursor material for the CVD process.The second material of the sacrificial layers 42 can be formed, forexample, CVD or atomic layer deposition (ALD).

The sacrificial layers 42 can be suitably patterned so that conductivematerial portions to be subsequently formed by replacement of thesacrificial layers 42 can function as electrically conductiveelectrodes, such as the control gate electrodes of the monolithicthree-dimensional NAND string memory devices to be subsequently formed.The sacrificial layers 42 may comprise a portion having a strip shapeextending substantially parallel to the major surface 9 of the substrate8.

The thicknesses of the insulator layers 32 and the sacrificial layers 42can be in a range from 20 nm to 50 nm, although lesser and greaterthicknesses can be employed for each insulator layer 32 and for eachsacrificial layer 42. The number of repetitions of the pairs of aninsulator layer 32 and a sacrificial layer (e.g., a control gateelectrode or a sacrificial material layer) 42 can be in a range from 2to 1,024, and typically from 8 to 256, although a greater number ofrepetitions can also be employed. The top and bottom gate electrodes inthe stack may function as the select gate electrodes. In one embodiment,each sacrificial layer 42 in the alternating stack (32, 42) can have auniform thickness that is substantially invariant within each respectivesacrificial layer 42.

A lithographic material stack (not shown) including at least aphotoresist layer can be formed over the alternating stack (32, 42), andcan be lithographically patterned to form openings therein. The patternin the lithographic material stack can be transferred through theentirety of the alternating stack (32, 42) by at least one anisotropicetch that employs the patterned lithographic material stack as an etchmask. Portions of the alternating stack (32, 42) underlying the openingsin the patterned lithographic material stack are etched to form memoryopenings. In other words, the transfer of the pattern in the patternedlithographic material stack through the alternating stack (32, 42) formsthe memory opening through the alternating stack (32, 42). The chemistryof the anisotropic etch process employed to etch through the materialsof the alternating stack (32, 42) can alternate to optimize etching ofthe first and second materials in the alternating stack (32, 42). Theanisotropic etch can be, for example, a series of reactive ion etches.Optionally, a sacrificial etch stop layer (not shown) may be employedbetween the alternating stack (32, 42) and the substrate 8. Thesidewalls of the memory openings can be substantially vertical, or canbe tapered. The patterned lithographic material stack can besubsequently removed, for example, by ashing.

Any remaining portion of the bottommost first material layer 32underneath each memory opening is subsequently etched so that the memoryopenings extend from the top surface of the alternating stack (32, 42)to the top surface of the first electrodes 12 or the substratesemiconductor layer 10.

As used herein, a first element “overlies” a second element if a firsthorizontal plane including the bottommost point of the first element iswithin, or above, a second horizontal plane including a topmost point ofthe second element and if there exits an areal overlap between the areaof the first element and the area of the second element in a see-throughview along a direction perpendicular to the first and second horizontalplanes. If a first element overlies a second element, the second element“underlies” the first element. In one embodiment, the entire area of amemory opening can be within the area of an underlying first electrode12 or the substrate semiconductor layer 10.

In one embodiment, an overetch into the first electrodes 12 or thesubstrate semiconductor layer 10 can be optionally performed after thetop surfaces of the first electrodes 12 or the substrate semiconductorlayer 10 are physically exposed. The overetch may be performed prior to,or after, removal of the lithographic material stack 45. The overetchcan be an anisotropic etch, and recesses the physically exposed portionsof the top surfaces of the first electrodes 12 or the substratesemiconductor layer 10 underlying the memory openings by a recess depth.In other words, the recessed surfaces of the first electrodes 12 or thesubstrate semiconductor layer 10 can be vertically offset from theundressed top surfaces of the first electrodes 12 or the substratesemiconductor layer 10 by the recess depth. The recess depth can be, forexample, in a range from 1 nm to 50 nm, although lesser and greaterrecess depths can also be employed. The overetch is optional, and may beomitted. In this case, the bottom surface of each memory opening can becoplanar with the topmost surface of the first electrodes 12, and/or thetopmost surface of the substrate 8.

Each of the memory openings can include a sidewall (or a plurality ofsidewalls) that extends substantially perpendicular to the major surfaceof the substrate 8 and is defined by the physically exposed sidewallsurfaces of the alternating stack (32, 42). Each of the memory openingscan further include a bottom surface that is a top surface of a firstelectrode 12 or the substrate semiconductor layer 10. In one embodiment,the sidewalls of the first electrodes 12, which are present around therecesses within the first electrodes 12, can be vertically coincidentwith the sidewalls of the memory openings. As used herein, a firstsurface is “vertically coincident” with a second surface if there existsa vertical plane including both the first surface and the secondsurface. Such a vertical plane may, or may not, have a horizontalcurvature, but does not include any curvature along the verticaldirection, i.e., extends straight up and down.

A channel and memory structure 55 can be formed within each memoryopening through the alternating stack (32, 42). The channel and memorystructures 55 can be formed, for example, by depositing a memory filmlayer in the memory openings and over the alternating stack (32, 42),and by anisotropically etching the memory film layer. The memory filmlayer can be a stack of contiguous material layers that overlie theentirety of the alternating stack (31, 42). The memory film layercontacts all sidewall surface(s) and all bottom surface(s) of the memoryopenings. The memory film layer is a contiguous film stack that providesthe functionality of charge storage in the absence of an externalelectrical bias voltage, while enabling charge transfer in the presenceof a suitable external electrical bias voltage.

In one embodiment, the memory film layer can be a stack, in the order offormation, of a blocking dielectric layer, a charge storage layer, and atunnel dielectric layer. In one embodiment, a plurality of floatinggates or a charge storage dielectric can be located between thetunneling dielectric layer and the blocking dielectric layer.

The blocking dielectric layer contacts the sidewalls of the memoryopenings. Specifically, the blocking dielectric layer can contact thesidewalls of the sacrificial layers 42. The blocking dielectric layermay include one or more dielectric material layers that can function asthe dielectric material(s) of a control gate dielectric between thesacrificial layers 42 and charge storage regions to be subsequentlyformed out of the charge storage layer. The blocking dielectric layercan include silicon oxide, a dielectric metal oxide, a dielectric metaloxynitride, or a combination thereof. In one embodiment, the blockingdielectric layer can include a stack of at least one silicon oxide layerand at least one dielectric metal oxide layer. The blocking dielectriclayer can be formed by a conformal deposition process such as chemicalvapor deposition (CVD) and/or atomic layer deposition (ALD), and/or bydeposition of a conformal material layer (such as an amorphous siliconlayer) and subsequent conversion of the conformal material layer into adielectric material layer (such as a silicon oxide layer). The thicknessof the blocking dielectric layer can be in a range from 6 nm to 24 nm,although lesser and greater thicknesses can also be employed.Alternatively, the blocking dielectric layer may be omitted from thememory opening, and instead be formed through the backside contacttrench in recesses formed by removal of the sacrificial layers 42 priorto forming the metal control gate electrodes through the backsidecontact trench.

The charge storage layer includes a dielectric charge trapping material,which can be, for example, silicon nitride, or a conductive materialsuch as doped polysilicon or a metallic material. In one embodiment, thecharge storage layer includes silicon nitride. The charge storage layercan be formed as a single charge storage layer of homogeneouscomposition, or can include a stack of multiple charge storage materiallayers. The multiple charge storage material layers, if employed, cancomprise a plurality of spaced-apart floating gate material layers thatcontain conductive materials (e.g., metal such as tungsten, molybdenum,tantalum, titanium, platinum, ruthenium, and alloys thereof, or a metalsilicide such as tungsten silicide, molybdenum silicide, tantalumsilicide, titanium silicide, nickel silicide, cobalt silicide, or acombination thereof) and/or semiconductor materials (e.g.,polycrystalline or amorphous semiconductor material including at leastone elemental semiconductor element or at least one compoundsemiconductor material). Alternatively or additionally, the chargestorage layer may comprise an insulating charge trapping material, suchas one or more silicon nitride segments. Alternatively, the chargestorage layer may comprise conductive nanoparticles such as metalnanoparticles, which can be, for example, ruthenium nanoparticles. Thecharge storage layer can be formed, for example, by chemical vapordeposition (CVD), atomic layer deposition (ALD), physical vapordeposition (PVD), or any suitable deposition technique for the selectedmaterial(s) for the charge storage layer. The thickness of the chargestorage layer can be in a range from 2 nm to 20 nm, although lesser andgreater thicknesses can also be employed.

The tunnel dielectric layer includes a dielectric material through whichcharge tunneling can be performed under suitable electrical biasconditions. The charge tunneling may be performed through hot-carrierinjection or by Fowler-Nordheim tunneling induced charge transferdepending on the mode of operation of the monolithic three-dimensionalNAND string memory device to be formed. The tunneling dielectric layercan include silicon oxide, silicon nitride, silicon oxynitride,dielectric metal oxides (such as aluminum oxide and hafnium oxide),dielectric metal oxynitride, dielectric metal silicates, alloys thereof,and/or combinations thereof. In one embodiment, the tunneling dielectriclayer can include a stack of a first silicon oxide layer, a siliconoxynitride layer, and a second silicon oxide layer, which is commonlyknown as an ONO stack. In one embodiment, the tunneling dielectric layercan include a silicon oxide layer that is substantially free of carbonor a silicon oxynitride layer that is substantially free of carbon. Thethickness of the tunnel dielectric layer can be in a range from 2 nm to20 nm, although lesser and greater thicknesses can also be employed.

Optionally, a permanent channel material layer (such as a polysiliconlayer) and/or a sacrificial layer (such as a dielectric material layer)may be formed on the memory film layer. The memory film layer (and anyadditional layer such as a permanent channel material layer or asacrificial layer) can be anisotropically etched so that horizontalportions of the memory film layer (and any additional layer) are removedfrom above the top surface of the alternating stack (32, 42) and at thebottom of each memory opening. Each remaining vertical portion of thememory film layer that remains within a memory opening after theanisotropic etch constitutes a memory film 50. Each memory film 50 canbe homeomorphic to a torus. As used herein, an element is homeomorphicto a geometrical shape if the shape of the element can be mapped to thegeometrical shape by continuous deformation without creation ordestruction of any hole. If the first electrode 12 underlies the memoryopenings, a top surface of the first electrode 12 can be physicallyexposed within the cavity defined by the inner sidewalls of an overlyingmemory film 50.

A semiconductor channel 60 can be formed on inner sidewalls of eachmemory film 50 by deposition of a semiconductor material layer and asubsequent anisotropic etch of the semiconductor material layer. Thesemiconductor material layer can include a doped polycrystallinesemiconductor material (such as doped polysilicon), or can include adoped amorphous semiconductor material (such as amorphous silicon) thatcan be subsequently converted into a doped polycrystalline semiconductormaterial after a suitable anneal at an elevated temperature.

Optionally, a dielectric core 62 can be formed within a cavity insideeach semiconductor channel 60, for example, by deposition of adielectric material such as silicon oxide, and subsequent planarizationof the dielectric material. The planarization of the dielectric materialremoves the portion of the deposited dielectric material from above thetop surface of the horizontal plane including the top surface of thealternating stack (32, 42). The planarization of the dielectric materialcan be performed, for example, by chemical mechanical planarization.Each remaining portion of the dielectric material inside a memoryopening constitutes a dielectric core 62. The dielectric core 62 is anoptional component, and a combination of a memory film 50 and asemiconductor channel 60 may completely fill a memory opening. A set ofa memory film 50, a semiconductor channel 60, and a dielectric core 62within a same memory opening constitutes a channel and memory structure55.

Drain regions 63 can be formed by recessing a top portion of eachdielectric core and depositing a doped semiconductor material. The dopedsemiconductor material can be, for example, doped polysilicon. Excessportions of the deposited semiconductor material can be removed fromabove the top surface of the alternating stack (32, 42), for example, bychemical mechanical planarization (CMP) or a recess etch.

Optionally, at least one dielectric support pillar 38 may be formedthrough the alternating stack (32, 42). As an optional structure, the atleast one dielectric support pillar 38 may, or may not, be presentwithin the first exemplary structure. In one embodiment, a dielectricsupport pillar 38 can be formed at each boundary between a first deviceregion in which replacement of the portions of the sacrificial layers 42therein with electrically conductive electrodes is desired and a seconddevice region in which replacement of the portions of the sacrificiallayers 42 therein with electrically conductive electrodes is notdesired.

A mask layer 36 can be formed over the alternating stack (32, 42), thechannel and memory structures 55, and the drain regions 63. The masklayer 36 functions as a mask during a subsequent etch process, and assuch, can be a hard mask layer. The mask layer 36 can be a dielectricmaterial layer including a material that is different from the secondmaterial, i.e., the material of the sacrificial layers 42. The masklayer 36 can include a dielectric material such as a dielectric metaloxide (such as Al₂O₃, HfO₂, and LaO₂), dopes silicate glass, undopedsilicate glass. The mask layer 36 can be deposited, for example, bychemical vapor deposition. The thickness of the mask layer 36 can be ina range from 30 nm to 1,000 nm, although lesser and greater thicknessescan also be employed.

Referring to FIG. 2, a photoresist layer 45 (and optionally additionallithographic material layers such as an organic planarization layerand/or an antireflective coating layer) can be formed over the topsurface of the mask layer 36. The photoresist layer 45 can belithographically patterned to form a plurality of openings therein. Theplurality of openings in the photoresist layer 45 can be formed in areasin which formation of contact openings is desired. As used herein, acontact opening refers to a cavity having sidewalls that extend from,and adjoin, a top surface of a structure and extend to a depth withinthe structure. The bottom of a contact opening may have a surfacevertically recessed from the top surface of the structure, or can havean opening that is connected to another cavity underlying the contactopening. A contact opening as initially formed may be a cavity having anopening, and can be subsequently filled with at least one materialportion.

The locations of the openings in the photoresist layer 45 can beselected to include areas of the electrically conductive via contacts tobe subsequently formed and to extend to different levels of thealternating stack (32, 42). As used herein, a “level” of a structureincluding alternating layers is defined as the relative position of aunit of repetition, which is a pair of a first material layer and asecond material layer, within the structure. Each adjoining pair of afirst material layer and a second material layer within a structurecontaining the alternating layers can be assigned an integer selectedfrom a set of positive integers such that the assigned integer increasesby 1, or decreases by one, as one counts each pair of the first andsecond material layers from one end of the structure to the opposite endof the structure. Each integer corresponds to a level (e.g., level 1)within the structure.

The pattern in the openings of the photoresist layer 45 can betransferred into the mask layer 36 by an etch, which can be ananisotropic etch that employs the photoresist layer 45 as an etch mask.For example, the anisotropic etch can be a reactive ion etch. Upontransfer of the pattern in the photoresist layer 45 through the masklayer 36, a plurality of openings 59 is formed within the mask layer 36.The plurality of openings can form a two dimensional array of openingsthat extend along two different horizontal directions.

For the purpose of facilitating description of the various embodimentsof the present disclosure, the different levels of the material layersof the present disclosure are assigned different level names. Thetopmost layer among the insulator layers 32 is herein referred to as atopmost insulator layer 32T. In an alternating stack (32, 42) includinga total of N sacrificial layers, the sacrificial layer 42 contacting thebottom surface of the topmost insulator layer 32T is herein referred toas a first-from-top sacrificial layer 42A or an N-th-from-bottomsacrificial layer. The insulator layer 32 contacting the bottom surfaceof the first-from-top sacrificial layer 42A (which is theN-th-from-bottom sacrificial layer) is herein referred to as afirst-from-top insulator layer 32A. The first-from-top sacrificial layer42A and the first-from-top insulator layer 32A collectively constitute afirst-from-top level or an N-th-from-bottom level. For every integer ithat is greater than 1 and not greater than the total number N of thesacrificial layers 42 in the alternating stack (32, 42), the sacrificiallayer 42 contacting the bottom surface of the (i−1)-th insulator layeris herein referred to as the i-th-from-top sacrificial layer or the(N+1−i)-th-from-bottom sacrificial layer. Similarly, for every integer ithat is greater than 1 and not greater than the total number of thesacrificial layers 42 in the alternating stack (32, 42), the insulatorlayer 32 contacting the bottom surface of the i-th sacrificial layer isherein referred to as the i-th-from-top insulator layer or the(N+1−i)-th-from-bottom insulator layer. If a total of N sacrificiallayers 42 exist in the alternating stack (32, 42), the N-th insulatorlayer is the insulator layer that is the most proximal to the substrate8 among the insulator layers 32 in the alternating stack (32, 42).

Thus, the alternating stack (32, 42) includes, from top to bottom, atopmost insulator layer 32T, a first-from-top sacrificial layer 42A, afirst-from-top insulator layer 32A, a second-from-top sacrificial layer42B, a second-from-top insulator layer 32B, an alternating stackincluding at least one intermediate sacrificial layer 42C and at leastone intermediate insulator layer 32C, an (N−2)-th-from-top sacrificiallayer 42D, an (N−2)-th-from-top insulator layer 32D, an(N−1)-th-from-top sacrificial layer 42E, an (N−2)-th-from-top insulatorlayer 32E, an N-th-from-top sacrificial layer 42F, and an N-th-from-topinsulator layer 32F. It is understood that an insulator layer 32 canrefer to any of, or each of, the various insulator layers (32A, 32B,32C, 32D, 32E, 32F), and a sacrificial layer 42 can refer to any of, oreach of, the various sacrificial layers (42A, 42B, 42C, 42D, 42E, 42F).Further, insulator layers 32 can refer to any plurality of, or all of,the various insulator layers (32A, 32B, 32C, 32D, 32E, 32F), andsacrificial layers 42 can refer to any plurality of, or all of, thevarious sacrificial layers (42A, 42B, 42C, 42D, 42E, 42F).

The plurality of openings 59 in the mask layer 36 can include at leastone first opening 59A that is formed in each area in which it is desiredto form a contact opening that extends to the N-th-from-top sacrificiallayer 42F upon full formation, i.e., at the end of processing steps thatcompletes formation of the contact opening. The N-th-from-topsacrificial layer 42F is the sacrificial layer 42 that is most proximalto the substrate 8 and most distal from the top surface of thealternating stack (32, 42). The plurality of openings 59 in the masklayer 36 can further include at least one second opening 59B that isformed in each area in which it is desired to form a contact openingthat extends to the (N−1)-th-from-top sacrificial layer 42E upon fullformation. The plurality of openings 59 in the mask layer 36 can furtherinclude at least one third opening 59C that is formed in each area inwhich it is desired to form a contact opening that extends to the(N−2)-th-from-top sacrificial layer 42D upon full formation. Theplurality of openings 59 in the mask layer 36 can further include atleast one intermediate-level opening 59D that formed in each area inwhich it is desired to form a contact opening that extends to asacrificial layer 42 located between the (N−2)-th-from-top sacrificiallayer 42D and the second-from-top sacrificial layer 42B upon fullformation. The plurality of openings 59 in the mask layer 36 can furtherinclude at least one (N−1)-th opening 59E that formed in each area inwhich it is desired to form a contact opening that extends to thesecond-from-top sacrificial layer 42B upon full formation. The pluralityof openings 59 in the mask layer 36 can further include at least N-thopening 59F that formed in each area in which it is desired to form acontact opening that extends to the first-from-top sacrificial layer 42Aupon full formation.

In one embodiment, the plurality of openings 59 can be arranged as alinear array such that each opening in the mask layer 36 thatcorresponds to a contact opening to extend to a deeper depth upon fullformation is located to a predetermined side of the linear array withrespect to any opening in the mask layer that corresponds to a contactopening to extend to a shallower depth upon full formation. In oneembodiment, the plurality of openings 59 can be periodic along onedirection such that the pitch between each neighboring pair of openings59 is the same. In one embodiment, the pitch between each neighboringpair of openings 59 is can increase along one direction with theincrease in the target depth of the corresponding contact openings inorder to prevent electrical shorts due to lateral broadening of contactopenings with depth.

Referring to FIG. 3, a layer of a slimming material is formed over themask layer 36. The layer of the slimming material is herein referred toas a slimming layer 47. The slimming layer 47 includes a slimmingmaterial which refers to a material that can be trimmed in multipletrimming processes. As used herein, a “trimming” process refers to aprocess in which peripheral portions of a structure is removed whileanother portion located inside the peripheral portion remains after theend of the process. The slimming layer 47 can be, for example, aphotoresist layer, an organic material layer, a dielectric materiallayer, or a semiconductor material layer. The thickness of the slimminglayer 47, as measured from the top surface of the mask layer 36, can begreater than the lateral extent of the plurality of openings 59 along ahorizontal direction that encompasses all types of openings (59A, 59B,59C, 59D, 59E, 59F) that correspond to different depths of contactopenings to be subsequently formed.

In one embodiment, the slimming layer 47 can be a photoresist layer. Inanother embodiment, the slimming layer 47 can be an organic materiallayer including an organic material that can be trimmed, for example, bya wet etch employing a solvent. In yet another embodiment, the slimminglayer 47 can be a dielectric material layer that includes a dielectricmaterial that is different from the materials of the mask layer 36 andthe insulator layers 32 and can be uniformly etched or recessed by a wetetch or a dry etch. In still another embodiment, the slimming layer 47can be a semiconductor material layer that includes a semiconductormaterial that can be uniformly etched or recessed by a wet etch or a dryetch. The thickness of the slimming layer 47 can be in a range from 1micron to 10 microns, although lesser and greater thicknesses can alsobe employed. In one embodiment, the slimming layer 47 can be aphotoresist layer having a thickness in a range from 2 microns to 5microns.

Referring to FIG. 4, the slimming layer 47 can be patterned tophysically expose the at least one first opening 59A (See FIG. 3), whileall other openings (59B, 59C, 59D, 59E, 59F) are covered by a remainingportion of the slimming layer 47. If the slimming layer 47 is aphotoresist layer, the slimming layer 47 can be lithographicallypatterned, i.e., by a combination of lithographic exposure anddevelopment. If the slimming layer 47 is not a photoresist layer, theslimming layer 47 can be patterned by application of a photoresist layerthereupon, lithographic patterning of the photoresist layer, and etchingof the portions of the slimming layer 47 that is not covered by theremaining portion of the photoresist layer, for example, by ananisotropic etch. The photoresist layer may be removed after patterningthe slimming layer 47. A remaining portion of the slimming layer 47fills each opening (59B, 59C, 59D, 59E, 59F) in the mask layer 36 exceptthe at least one first opening 59A.

Each portion of the topmost insulator layer 32 underlying the at leastone first opening is anisotropically etched employing the combination ofthe mask layer 36 and the slimming layer 47 as an etch mask. A firstcontact opening 69A is formed through the mask layer 36 and the topmostinsulator layer 32 within each area of the at least one first opening59A in the mask layer 36. In one embodiment, the chemistry of theanisotropic etch can be selected such that the bottom surface of eachfirst contact opening 69A is formed at the top surface of, or betweenthe top surface and the bottom surface of, or at the bottom surface oftopmost insulator layer 32 at the end of the processing steps of FIG. 4.In one embodiment, the chemistry of the anisotropic etch can beselective to the second material, i.e., the material of the sacrificiallayers 42. In this case, the bottom surface of each first contactopening 69A can be formed at the top surface of the first-from-topsacrificial layer 42A. Alternately, the anisotropic etch process caninclude multiple steps so that portions of the topmost insulator layer32 and the first-from-top sacrificial layer 42A underlying each firstopening 59A (See FIG. 3) can be etched by the anisotropic etch. In thiscase, the bottom surface of each first contact opening 69A can be formedat the top surface of the first-from-top insulator layer 32A, which iscoplanar with the bottom surface of the first-from-top sacrificial layer42A.

Referring to FIG. 5, a trimming process is performed to trim theslimming layer 47. A physically exposed peripheral portion including atop portion of the slimming layer 47 and a sidewall portion thatoverlies the at least one second opening 59B (See FIG. 4) can be removedby the slimming process, while all other openings (59C, 59D, 59E, 59F)other than the at least one first and second openings (59A, 59B) arecovered by the remaining portion of the slimming layer 47. The trimmingprocess can vary depending on the nature of the slimming material in theslimming layer 47. For example, if the slimming layer 47 includes aphotoresist layer, the trimming process can be an ashing process inwhich the ashing rate is limited by the supply of oxidizing agents (suchas oxygen). Alternatively, the trimming process can be a wet etchprocess or a dry etch process in which the rate of removal of theslimming material is limited by the process time during which theslimming material is physically exposed to an etchant or a solvent. Theslimming material is partially removed to reduce a lateral extentthereof and a thickness thereof during the trimming process.

An anisotropic etch process is performed to vertically extend the atleast one first contact opening 69A downward through a pair of asacrificial layer 42 and an insulator layer 32. If the bottom surface ofeach first contact opening 69A is located at the top surface of thefirst-from-top sacrificial layer 42A at the end of the processing stepsof FIG. 4, the bottom surface of each first contact opening 69A isrecessed through the first-from-top sacrificial layer 42A during a firststep of the anisotropic etch, and then further recessed through thefirst-from-top insulator layer 32A during a second step of theanisotropic etch. During the second step, a second contact opening 69Bcan be formed through the physically exposed openings in the mask layer36 and the topmost insulator layer 32 concurrently with the recessing ofthe first contact opening(s) 69A through the first-from-top insulatorlayer 32A. Each second contact opening 69B can be formed within an areaof a second opening 59B within the mask layer 36.

If the bottom surface of each first contact opening 69A is located atthe top surface of the first-from-top insulator layer 32A at the end ofthe processing steps of FIG. 4, the bottom surface of each first contactopening 69A is recessed through the first-from-top insulator layer 32Aduring a first step of the anisotropic etch, and then further recessedthrough the second-from-top sacrificial layer 42B during a second stepof the anisotropic etch. During the first step, a second contact opening69B can be formed through the mask layer 36 and the topmost insulatorlayer 32 concurrently with the recessing of the first contact opening(s)69A through the first-from-top insulator layer 32A. During the secondstep, the second contact opening 69B can be recessed through thefirst-from-top sacrificial layer 42A concurrently with the recessing ofthe first contact opening(s) 69A through the second-from-top sacrificiallayer 42B. Each second contact opening 69B can be formed within an areaof a second opening 59B within the mask layer 36. A cycle of a trimmingprocess and an etch process has the effect of increasing the totalnumber of contact openings 69 and extending the depth of eachpre-existing contact opening 69. The depth of each contact opening 69 ismeasured from the periphery of the topmost portion of the contactopening 69, i.e., from the horizontal plane including the top surface ofthe mask layer 36.

Referring to FIG. 6, additional contact openings (69C, 69D, 69E) can beformed and the depths of pre-existing contact openings (69A, 69B) can bevertically extended by iteratively, and alternately, performing etchprocesses and trimming processes. The processing conditions of eachtrimming processes and etch processes can be substantially the same asin the corresponding trimming process and the corresponding etch processof FIG. 5. Portions of the alternating stack (32, 42) located underneathopenings 59 (See FIG. 3) that are not covered by the slimming materialare etched in each of the etch processes. A total number of openings 59not covered by the slimming material can increase in each of thetrimming processes by partial removal of the slimming material.

Each contact opening 69 that is present at an end of a previous etchprocess vertically extends downward during the next etch process by thetotal thickness of a pair of a sacrificial layer 42 and an insulatorlayer 32 that is located immediately below the contact opening 69 at theend of the previous etch process. Each etch process extends the depth ofeach pre-existing contact opening 69 by the total thickness of a pair ofa sacrificial layer 42 and an insulator layer 32 that is locatedimmediately below the respective pre-existing contact opening 69.

In general, the plurality of contact openings 69 can be formed bysimultaneously etching a portion of a first insulator layer 32 (e.g., an(i+1)-th-from-top insulator layer 32 in which i is less than N) in thealternating stack (32, 42) within an area of a first contact opening 69Aand a portion of a second insulator layer 32 (e.g., an i-th-from-topinsulator layer 32) in the alternating stack (32, 42) within an area ofa second contact opening 69B. The second insulator layer is verticallyspaced from the first insulator layer by at least one sacrificial layer42 in the alternating stack (32, 42).

Further, the plurality of contact openings 69 can be formed bysimultaneously etching a portion of a first sacrificial layer 42 (e.g.,an (i+1)-th-from-top sacrificial layer 42 in which i is less than N) inthe alternating stack (32, 42) within an area of a first contact opening69A and a portion of a second sacrificial layer 42 (e.g., ani-th-from-top sacrificial layer 42) in the alternating stack (32, 42)within an area of a second contact opening 69B. The second sacrificiallayer 42 is vertically spaced from the first sacrificial layer 42 by atleast one insulator layer 32 in the alternating stack (32, 42).

For example, a portion of a first sacrificial layer 42 (e.g., the i-thfrom-top sacrificial layer 42 in which i is less than N) underlying afirst opening 59A (See FIG. 2) and having a top surface that isphysically exposed to a first contact opening 69A can be etched during astep of an etch process so that the bottom surface of the first contactopening 69A extends to a top surface of a first insulator layer 32(e.g., the i-th-from-top insulator material layer 32) that is locatedunder the first sacrificial layer 42 in the alternating stack (32, 42).In this case, a portion of a second sacrificial layer (e.g., the(i−1)-th from-top sacrificial layer 42) underlying a second opening 59B(See FIG. 2) and having a top surface that is physically exposed to asecond contact opening 69B can be etched during the same step of thesame etch process so that the bottom surface of the second contactopening 69B extends to a top surface of a second insulator layer 32(e.g., the (i−1)-th-from-top insulator layer 32) that is located underthe second sacrificial layer 42 in the alternating stack (32, 42).Likewise, a portion of a third sacrificial layer (e.g., the (i−2)-thfrom-top sacrificial layer 42) underlying a third opening 59C (See FIG.2) and having a top surface that is physically exposed to a thirdcontact opening 69C can be etched during the same step of the same etchprocess so that the bottom surface of the third contact opening 69Bextends to a top surface of a third insulator layer 32 (e.g., the(i−2)-th-from-top insulator layer 32) that is located under the thirdsacrificial layer 42 in the alternating stack (32, 42).

Further, a portion of the first insulating layer 32 (e.g., the i-thfrom-top insulator layer 32 in which i is less than N) underlying thefirst opening 59A (See FIG. 2) and having a top surface that isphysically exposed to the first contact opening 69A can be etched duringanother step of the same etch process within the same cycle so that thebottom surface of the first contact opening 69A extends to a top surfaceof another sacrificial layer 42 (e.g., the (i+1)-th-from-top sacrificiallayer 42) that is located under the first insulating layer 32 in thealternating stack (32, 42). In this case, a portion of the secondinsulating layer 32 (e.g., the (i−1)-th from-top insulator layer 32)underlying the second opening 59B (See FIG. 2) and having a top surfacethat is physically exposed to the second contact opening 69B can beetched during this step of the same etch process so that the bottomsurface of the second contact opening 69B extends to a top surface ofthe first sacrificial layer 42 (e.g., the i-th-from-top sacrificiallayer 42) that is located under the second insulating layer 32 in thealternating stack (32, 42). Likewise, a portion of the third insulatinglayer 32 (e.g., the (i−2)-th from-top insulator layer 32) underlying thethird opening 59C (See FIG. 2) and having a top surface that isphysically exposed to the third contact opening 69C can be etched duringthis step of the same etch process so that the bottom surface of thethird contact opening 69C extends to a top surface of the secondsacrificial layer 42 (e.g., the (i−1)-th-from-top sacrificial layer 42)that is located under the third insulating layer 32 in the alternatingstack (32, 42).

In one embodiment, the etch chemistry for the step of etching thematerial of the sacrificial layers 42 can be selective to the materialof the insulator layers 32, and the etch chemistry for the step ofetching the material of the insulator layers 32 can be selective to thematerial of the sacrificial layers 42. Under such conditions, therecessing of the bottom surfaces of the contact openings 69 during aprocessing step that etches one type of material, i.e., the firstmaterial of the insulator layers 32 or the second material of thesacrificial layers 42, can be self-stopping on the top surface of theimmediately underlying material.

During each trimming process, surface portions of the slimming layer 47are removed from the top surface and the sidewalls of the slimming layer47 to physically expose at least one additional opening 59 in the masklayer 36. During the partial removal of the slimming layer 47, thethickness and the lateral extent of the slimming layer 47 can besimultaneously reduced. In one embodiment, the sidewalls of the slimminglayer 47 be laterally recessed from all horizontal directions and thetop surface of the slimming layer 47 can be recessed at the same rate asthe recess rate of a sidewall of the slimming layer 47. In this case,the lateral extent of the slimming layer 47 can be reduced twice at therate of reduction of the thickness of the slimming layer 47. The rate oftrimming of the slimming layer 47 can be selected such that one trimmingprocess physically exposes one new set of openings 59 in the mask layer36 that correspond to areas of contact openings designed 69 to extend toa same level, e.g., to a same sacrificial layer 42 upon completion offormation of the respective contact openings 69.

In one embodiment, the plurality of contact openings 69 can be formed asmultiple sets of linearly positioned contact openings 69. For example, aplurality of first contact openings 69A can be formed in a first linearconfiguration, and a plurality of i-th contact openings 69 can be formedin an i-th linear configuration that extends along the horizontaldirection of the plurality of first contact openings 69A for everyinteger i greater than 1 and not greater than N, which is the totalnumber of the sacrificial layers 42. As used herein, a “linearconfiguration” refers to a configuration in which multiple elements arelocated at positions laterally spaced from one another such that astraight line passing through the multiple elements exists.

Multiple linear sets of contact openings 69 can be formed such that eachlinear set of contact openings 69 has the same depth, while contactopenings belonging to different linear sets have different depths. Eachlinear set of contact openings 69 having the same depth can laterallyextend along a first horizontal direction. Different linear sets ofcontact openings 69 can laterally extend along a second horizontaldirection that is different from the first horizontal direction. In oneembodiment, the second horizontal direction can be orthogonal to thefirst horizontal direction.

While the present disclosure has been described employing an embodimentin which a step for etching the second material of the sacrificiallayers 42 precedes a step for etching the first material of theinsulator layers 32 in an etch process within each cycle of a trimmingprocess and an etch process, an alternative embodiment is expresslycontemplated herein, in which a step for etching the first material ofthe insulator layers 32 precedes a step for etching the second materialof the sacrificial layers 42 in an etch process within each cycle of atrimming process and an etch process. In this case, the last etchprocess that follows the last trimming process may include only the stepof etching the first material of the insulator layers 32, i.e., may notinclude a step for etching the second material of the sacrificial layers42.

A plurality of contact openings 69 is formed within the alternatingstack (32, 42). Each of the plurality of contact openings 69 extends atleast from the topmost surface of the alternating stack (32, 42), andspecifically from the top surface of the mask layer 36, to a surface ofa respective material layer. The respective material layers can includesacrificial layers 42 located at different levels within the alternatingstack (32, 42) in case each etch process terminates with a step thatetches the second material of the sacrificial layers 42. Alternatively,the respective material layers can include insulator layers 32 locatedat different levels within the alternating stack (32, 42) in case eachetch process terminates with a step that etches the first material ofthe insulator layers 32.

Referring to FIG. 7, the cycles of alternating processes that include atrimming process and an etch process continues until the entire set ofopenings 59 (See FIG. 2) in the mask layer 36 are physically exposedafter the trimming process of the last cycle, and the at least one N-thcontact opening 69F is formed through the topmost insulator layer 32.The entirety of the remaining portion of the slimming layer 47 can beremoved during the last trimming process. In one embodiment, all of theopenings 59 in the mask layer 36 can be physically exposed. Uponcompletion of the etch process after the last trimming process, aplurality of contact openings 69 extend through a respective opening inthe mask layer 36 from the top surface of the mask layer to a respectiveone of the plurality of sacrificial layers 42.

Upon termination of the processing steps of FIG. 7, any remainingportion of the slimming material layer 47, if present, is removed. Eachof the plurality of contact openings 69 can extend at least from thetopmost surface of the alternating stack (32, 42), and specifically fromthe top surface of the mask layer 36, to a surface of a respectivesacrificial layer 42. In one embodiment, the bottom surface of eachcontact opening 69 is a top surface a respective sacrificial layer 42.The top surface the respective sacrificial layer 42 can be the topmostsurface of the respective sacrificial layer 42 or a recessed surface ofthe respective sacrificial layer 42 that is vertically offset from thetopmost surface of the respective sacrificial layer 42 due to anoveretch or a finite selectivity of the last etch step that etches thefirst material of the insulator layers 32.

Thus, a first contact opening 69A among the plurality of contactopenings 69 has a bottom surface that is a top surface of a firstsacrificial layer 42 (e.g., the N-th-from-top sacrificial layer 42F) inthe alternating stack (32, 42), a second contact opening 69B among theplurality of contact openings 69 has a bottom surface that is a topsurface of a second sacrificial layer 42 (e.g., the (N−1)-th-from-topsacrificial layer 42E) in the alternating stack (32, 42), in which thesecond sacrificial layer 42 is different from the first sacrificiallayer 42. In general, an i-th contact opening 69 can have a bottomsurface that is a top surface of the (N+1−i)-th-from-top sacrificiallayer 42 in the alternating stack (32, 42).

The sidewall of the contact openings 69 can be vertical, substantiallyvertical, or tapered depending on the chemistries of the anisotropicetch processes employed during the cycles of a trimming process and anetch process. In one embodiment, the sidewalls of each contact opening69 can be smooth surfaces without substantial protrusions or recesses.The sidewalls of each first contact opening 69A include sidewalls of thetopmost insulator layer 32, sidewalls of each i-th-from-top sacrificiallayer 42 for each integer index i beginning from 1 and ending with N−1,and sidewalls of each j-th-from-top sacrificial layer 42 for eachinteger index j beginning from 1 and ending with N−1. For every positiveinteger k less than N, the sidewalls of each k-th contact opening 69include sidewalls of the topmost insulator layer 32, sidewalls of eachi-th-from-top sacrificial layer 42 for each integer index i beginningfrom 1 and ending with N-k, and sidewalls of each j-th-from-topsacrificial layer 42 for each integer index j beginning from 1 andending with N-k. The sidewalls of each N-th contact opening 69F includesidewall of the topmost insulator layer 32.

In one embodiment, at least one of the plurality of contact opening 69(e.g., a first contact opening 69A) can have a first periphery containedentirety within a sidewall of one of the sacrificial layers 42 (e.g.,the N-th-from-top sacrificial layer 42F) and a second peripherycontained entirely within a sidewall of another of the sacrificiallayers 42 (e.g., the (N−1)-th-from-top sacrificial layer 42E). As usedherein, a periphery is a closed line that is topologically homeomorphicto a circle. In one embodiment, at least one of the plurality of contactopening 69 (e.g., a first contact opening 69A) can have a firstperiphery contained entirety within a sidewall of one of the insulatorlayers 32 (e.g., the (N−1)-th-from-top insulator layer 32E) and a secondperiphery contained entirely within a sidewall of another of theinsulator layer 32 (e.g., the (N−2)-th-from-top sacrificial layer 42D).

Referring to FIG. 8, a photoresist layer 85 can be applied over the masklayer 36 and lithographically patterned to form openings in areas inwhich formation of peripheral device electrically conductive viacontacts 86 (See FIG. 15) is desired. The photoresist layer 85 can be aconformal photoresist layer that fills, partially or completely, allopenings under the topmost surface of the mask layer 36. The pattern inthe photoresist layer 85 can be transferred through the mask layer 36and the alternating stack (32, 42) and optionally through theplanarization material layer 208 employing an anisotropic etch to formvia trenches that extend to various conductive components thatconstitute electrical nodes of the at least one peripheral device 20.Each via trench that extends to the various components of the at leastone peripheral device 20 is a contact opening, and is herein referred toas a peripheral contact opening 89. The photoresist layer 85 can besubsequently removed, for example, by ashing.

Referring to FIG. 9, a contiguous insulating material layer 64L can beformed on physically exposed surfaces on an upper side of the firstexemplary structure, which include the top surface of the mask layer 36,the sidewalls of the plurality of contact openings 69, and the surfacesof the various sacrificial layers 42 underneath the plurality of contactopenings 69 (i.e., the bottom surfaces of the contact openings 69), thevarious sidewalls and bottom surfaces of the peripheral contact openings89. The contiguous insulating material layer 64L includes an insulatingmaterial that is different from the second material, i.e., the materialof the sacrificial layers 42. For example, the contiguous insulatingmaterial layer 64L can include silicon oxide or a dielectric metal oxidesuch as aluminum oxide, tantalum oxide, and/or hafnium oxide. Thecontiguous insulating material layer 64L can be deposited, for example,by a conformal deposition method such as chemical vapor deposition (CVD)or atomic layer deposition (ALD). The thickness of the contiguousinsulating material layer 64L, as measured at a bottom portion of afirst contact opening 69A, can be in a range from 1 nm to 60 nm,although lesser and greater thicknesses can also be employed. In oneembodiment, the thickness of the contiguous insulating material layer64L can be in a range from 3 nm to 30 nm.

Referring to FIG. 10, insulating liners 64 can be formed on eachsidewall of the plurality of contact openings 69 and on each sidewall ofthe peripheral contact openings 89 by performing an anisotropic etch ofthe contiguous insulating material layer 64L. Specifically, uponanisotropically etching the contiguous insulating material layer 64L,each remaining portion of the contiguous insulating material layer 64Lconstitutes an insulating liner 64. The insulating material of thecontiguous insulating material layer 64L is removed from each bottomportion of the plurality of contact openings 69 and the peripheralcontact openings 89. Thus, a portion of a top surface of a sacrificiallayer 42 is physically exposed at the bottom of each of the plurality ofcontact openings 69. Further, a top surface of a conductive element(e.g., a source region 201, a drain region 202, and a gate silicidewithin a gate stack 205) can be physically exposed at the bottom of eachof the peripheral contact openings 89. The insulating liners 64 can beformed simultaneously directly on the sidewalls of the plurality ofcontact openings 69 and directly on the sidewalls of the peripheralcontact openings 89. Each insulating liner 64 can be topologicallyhomeomorphic to a torus.

Referring to FIG. 11, a photoresist layer 77 can be applied over themask layer 36 and lithographically patterned to form at least onebackside contact trench 79 in an area in which formation of a backsidecontact 76 (See FIG. 15) is desired. The photoresist layer 77 can be aconformal photoresist layer that fills, partially or completely, allopenings under the topmost surface of the mask layer 36. The pattern inthe photoresist layer 77 can be transferred through the mask layer 36and the alternating stack (32, 42) employing an anisotropic etch to forma trench that extends at least to the top surface of the substrate 8.The trench that extends at least to the top surface of the substrate 8is a contact opening, and can be a source contact opening. In oneembodiment, electrical dopants (i.e., p-type dopants or n-type dopants)can be implanted into the portion of the doped well 14 (or the substratesemiconductor layer 10) to form a source region 12 for vertical memorydevices including the channel and memory structures 55. The photoresistlayer 77 can be subsequently removed, for example, by ashing.

Referring to FIG. 12, an etchant that selectively etches the secondmaterial of the sacrificial layers 42 with respect to the first materialof the insulator layers 32 can be introduced into the plurality ofcontact openings 69 and the at least one backside contact trench 79, forexample, employing an etch process. The removal of the second materialof the sacrificial layers 42 can be selective to the materials of theinsulating liners 64, the first material of the insulator layers 32, andthe material of the outermost layer of the memory films 50. Optionally,the removal of the second material of the sacrificial layers 42 can beselective to the material of the mask layer 36, and the variousconductive materials that are present underneath the peripheral contactopenings 89. The insulating liners 64 protect the sidewalls of each ofthe plurality of contact openings 69 from an etchant used to remove atleast a portion of each sacrificial layer 42.

The etch process that removes the second material selective to the firstmaterial and the outermost layer of the memory films 50 can be a wetetch process employing a wet etch solution, or can be a gas phase (dry)etch process in which the etchant is introduced in a vapor phase intothe plurality of contact openings 69 and the at least one backsidecontact trench 79. For example, if the sacrificial layers 42 includesilicon nitride, the etch process can be a wet etch process in which thefirst exemplary structure is immersed within a wet etch tank includingphosphoric acid, which etches silicon nitride selective to siliconoxide, silicon, and various other materials employed in the art. Theinsulating liners 64, the at least one dielectric support pillar 38 (ifpresent), the channel and memory structures 55, and the insulatinglayers 32 structurally support the first exemplary structure. The atleast one dielectric support pillar 38 may, or may not, be present.

Each contiguous portion of the sacrificial layers 42 having a topsurface that is physically exposed to one of the plurality of contactopenings 69 can be removed during the etch process to form a recess 41.Each recess 41 can be a laterally extending cavity having a lateraldimension that is greater than the vertical extent of the cavity. Aplurality of recesses 41 can be formed in the volumes from which thesecond material of the sacrificial layer 42 is removed. The memoryopenings in which the channel and memory structures 55 are formed areherein referred to as front side cavities, and the recesses 41 areherein referred to as back side cavities. In one embodiment, the deviceregion comprises an array of monolithic three dimensional NAND stringshaving a plurality of device levels disposed above the substrate 8. Inthis case, each recess 41 can define a space for receiving a respectiveword line of the array of monolithic three dimensional NAND strings.

Each of the plurality of recesses 41 can extending substantiallyparallel to the top surface of the substrate 8. In one embodiment, eachrecess 41 can be vertically bounded by a top surface of an underlyinginsulator layer 32 and a bottom surface of an overlying insulator layer32 except in regions at which the recess is connected to one of thecontact openings 69. In one embodiment, each recess 41 can have auniform height throughout. A bottom portion of each of the plurality ofcontact openings 69 can be connected to an underlying recess 41. Duringthe etch process that forms the plurality of recesses 41, the insulatingliners 64 can protect the sidewalls of the plurality of contact openings69. Thus, an insulating liner 64 can laterally separate a contactopening 69 from all recesses 41 that are located above the recess 41 towhich the contact opening 69 is contiguously connected to through abottom opening of the contact opening 69. The recesses 41 are formedacross multiple levels, and as a result, a first recess 41 formed byremoval of a portion of a first sacrificial layer 42 can be located at adifferent level than a second recess 41 formed by removal of a portionof a second sacrificial layer 42 that is different from the firstsacrificial layer 42.

Referring to FIG. 13, a conductive material can be simultaneouslydeposited in the plurality of contact openings 69 and the plurality ofrecesses 41, the backside contact trench 79, and the peripheral contactopenings 89, and over the top surface of the mask layer 36. Theconductive material is herein referred to as a first conductivematerial, or an electrically conductive electrode material. The firstconductive material can be deposited by a conformal deposition method,which can be, for example, chemical vapor deposition (CVD), atomic layerdeposition (ALD), electroless plating, electroplating, or a combinationthereof. The conductive material can be an elemental metal, anintermetallic alloy of at least two elemental metals, a conductivenitride of at least one elemental metal, a conductive metal oxide, aconductive doped semiconductor material, a conductivemetal-semiconductor alloy such as a metal silicide, alloys thereof, andcombinations or stacks thereof. Non-limiting exemplary conductivematerials that can be deposited in the plurality of contact openings 69and the plurality of recesses 41 include tungsten, tungsten nitride,titanium, titanium nitride, tantalum, and tantalum nitride. In oneembodiment, the electrically conductive electrode material can comprisea metal such as tungsten and/or metal nitride. In one embodiment, theconductive material for filling the plurality of contact openings 69,the plurality of recesses 41, and the peripheral contact openings 89 canbe selected from tungsten and a combination of titanium nitride andtungsten. In one embodiment, the conductive material can be deposited bychemical vapor deposition.

Simultaneous deposition of the conductive material in the plurality ofcontact openings 69 (See FIG. 12), in the plurality of recesses 41 (SeeFIG. 12), on the sidewalls and the bottom surface of the backsidecontact trench 79 (See FIG. 12), and over the top surface of the masklayer 36 forms a plurality of electrically conductive electrodes 46 inthe plurality of recesses 41 and a contiguous conductive material layer72L. Each electrically conductive electrode 46 can be a conductive linestructure. The contiguous conductive material layer 72L includesportions that fill all of the plurality of contact openings 69, aportion formed on the sidewalls of the bottom surface of the backsidecontact trench 79, and a portion overlying the top surface of the masklayer 36. The contiguous conductive material layer 72L and the pluralityof electrically conductive electrodes 46 are formed as an integralstructure, i.e., a single contiguous structure.

Referring to FIG. 14, the deposited conductive material is etched back,for example, by an isotropic etch. The portion of the contiguousconductive material layer 72L overlying the top surface of the masklayer 36 and the portion of the contiguous conductive material layer 72Llocated within the backside contact trench 79 are removed. Eachremaining portion of the deposited conductive material in the pluralityof contact openings 69 (See FIG. 12) constitutes an electricallyconductive via contact 66. Each remaining portion of the depositedconductive material in the recesses 41 (See FIG. 12) constitutes anelectrically conductive electrode 46. Each electrically conductiveelectrode 46 can be a conductive line structure. Each remaining portionof the deposited conductive material in a peripheral contact opening 89(See FIG. 12) constitutes a peripheral device electrically conductivevia contact 86.

Each of the plurality of electrically conductive via contacts 66 iselectrically shorted to an electrically conductive electrode 46, and canbe electrically isolated from all other electrically conductiveelectrodes 46. Each electrically conductive electrode 46 can beelectrically isolated from any other electrically conductive electrodes46 located at a different level, i.e., from any other electricallyconductive electrode 46 that overlies the electrically conductiveelectrode 46 and from any other electrically conductive electrode 46that underlies the electrically conductive electrode 46.

Each electrically conductive electrode 46 can function as a combinationof a plurality of control gate electrodes and a word line electricallyconnecting, i.e., electrically shorting, the plurality of control gateelectrodes. The plurality of control gate electrodes within eachelectrically conductive electrode 46 can include control gate electrodeslocated at the same level for the vertical memory devices including thechannel and memory structures 55. In other words, each electricallyconductive electrode 46 can be a word line that functions as a commoncontrol gate electrode for the plurality of vertical memory devices.

The plurality of electrically conductive via contacts 66 include atleast one first electrically conductive via contact 66A that is locatedwithin the volume of a first contact opening 69A (See FIG. 12) and iselectrically shorted to an electrically conductive electrode 46, whichcontacts the top surface of the N-th-from-top insulator layer 32F andthe bottom surface of the (N−1)-th-from-top insulator layer 32E, and isherein referred to as an N-th-from-top electrically conductive electrode46F or a first-from-bottom electrically conductive electrode.

The plurality of electrically conductive via contacts 66 can furtherinclude at least one second electrically conductive via contact 66B thatis located within the volume of a second contact opening 69B (See FIG.12) and is electrically shorted to an electrically conductive electrode46, which contacts the top surface of the (N−1)-th-from-top insulatorlayer 32E and the bottom surface of the (N−2)-th-from-top insulatorlayer 32D, and is herein referred to as an (N−1)-th-from-topelectrically conductive electrode 46E or a second-from-bottomelectrically conductive electrode. The plurality of electricallyconductive via contacts 66 can further include at least one thirdelectrically conductive via contact 66C that is located within thevolume of a third contact opening 69C (See FIG. 12) and is electricallyshorted to an electrically conductive electrode 46, which contacts thetop surface of the (N−2)-th-from-top insulator layer 32D and the bottomsurface of the (N−3)-th-from-top insulator layer, and is herein referredto as an (N−2)-th-from-top electrically conductive electrode 46D or athird-from-bottom electrically conductive electrode. The plurality ofelectrically conductive via contacts 66 can further include at least oneintermediate level electrically conductive via contact 66D that islocated within the volume of an intermediate contact opening 69D (SeeFIG. 12) and is electrically shorted to an electrically conductiveelectrode 46, which contacts the top surface of an immediatelyunderlying insulator layer 32 and the bottom surface of an immediatelyoverlying insulator layer 32, and is herein referred to as anintermediate electrically conductive electrode. The plurality ofelectrically conductive via contacts 66 can further include at least one(N−1)-th electrically conductive via contact 66E that is located withinthe volume of an (N−1)-th contact opening 69E (See FIG. 12) and iselectrically shorted to an electrically conductive electrode 46, whichcontacts the top surface of the second-from-top insulator layer 32B andthe bottom surface of the first-from-top insulator layer 32A, and isherein referred to as a second-from-top electrically conductiveelectrode 46B or an (N−1)-th-from-bottom electrically conductiveelectrode. The plurality of electrically conductive via contacts 66further includes at least one N-th electrically conductive via contact66F that is located within the volume of a first contact opening 69A(See FIG. 12) and is electrically shorted to a topmost electricallyconductive electrode 46, which contacts the top surface of thefirst-from-top insulator layer 32A and the bottom surface of the topmostinsulator layer 32, and is herein referred to as the first-from-topelectrically conductive electrode 46A or an N-th-from-bottomelectrically conductive electrode.

A first electrically conductive electrode 46 can be formed into a firstrecess 41 (e.g., the recess 41 located directly above the N-th-from-topinsulator layer 32F) through the backside contact trench 79 and thefirst contact opening 69A. A second electrically conductive electrode 46can be deposited into a second recess 41 (e.g., the recess 41 locateddirectly above the (N−1)-th-from-top insulator layer 32E) through thebackside contact trench 79 and the second contact opening 69B in thesame deposition step as depositing the first and the second electricallyconductive via contacts (66A, 66B). The first electrically conductiveelectrode 46 extends around the first contact opening 69A and the firstelectrically conductive via contact 66A is located in the first contactopening 69A. An insulating liner 64 located on the sidewall of the firstcontact opening 69 An electrically isolates the second electricallyconductive electrode 46 from the first electrically conductive viacontact 66A located in the first contact opening 69A. The firstelectrically conductive via contact 66A extends deeper than the secondelectrically conductive via contact 66B such that bottom surfaces of theplurality of electrically conductive via contacts (66A, 66B, 66C, 66D,66E, 66F) form a step pattern.

Thus, the alternating stack (32, 46) includes, from top to bottom, atopmost insulator layer 32T, a first-from-top electrically conductiveelectrode 46A, a first-from-top insulator layer 32A, a second-from-topelectrically conductive electrode 46B, a second-from-top insulator layer32B, an alternating stack including at least one intermediateelectrically conductive electrode 46C and at least one intermediateinsulator layer 32C, an (N−2)-th-from-top electrically conductiveelectrode 46D, an (N−2)-th-from-top insulator layer 32D, an(N−1)-th-from-top electrically conductive electrode 46E, an(N−2)-th-from-top insulator layer 32E, an N-th-from-top electricallyconductive electrode 46F, and an N-th-from-top insulator layer 32F. Itis understood that an insulator layer 32 can refer to any of, or eachof, the various insulator layers (32A, 32B, 32C, 32D, 32E, 32F), and anelectrically conductive electrode 46 can refer to any of, or each of,the various sacrificial layers (46A, 46B, 46C, 46D, 46E, 46F). Further,insulator layers 32 can refer to any plurality of, or all of, thevarious insulator layers (32A, 32B, 32C, 32D, 32E, 32F), andelectrically conductive electrodes 46 can refer to any plurality of, orall of, the various electrically conductive electrodes (46A, 46B, 46C,46D, 46E, 46F).

Remaining contiguous portions of the deposited conductive materialinclude a plurality of integrated line and via structures (46, 66).Specifically, each electrically shorted pair of an electricallyconductive via contact 66 and an electrically conductive electrode 46constitutes an integrated line and via structure (46, 66). The firstdevice structure includes a plurality of integrated line and viastructures (46, 66) having coplanar topmost surfaces (that are withinthe horizontal plane including the top surface of the mask layer 36) andbottommost surfaces located at different distances from the horizontalplane including the top surface of the alternating stack (32, 46) of theinsulator layers 32 and the electrically conductive electrodes 46. Inone embodiment, each instance of the electrically conductive electrodes46 can be a portion of a respective one of the plurality of integratedline and via structures (46, 66).

Optionally, each integrated line and via structure (46, 66) can includea metallic liner 461 that coats the entire surfaces of a contiguouscavity including a corresponding contact opening 69 and a correspondingrecess 41. For example, the metallic liners 461 can be a contiguouslayer of titanium nitride. Each integrated line and via structure (46,66) can include a conductive material portion 462 that can be embeddedwithin the metallic liner 461, or can contact the surfaces of insulatorlayers 32, or can contact a dielectric material liner (not shown) suchas a blocking dielectric layer that can be formed within the recesses 41and the dielectric liners 64 prior to formation of the integrated lineand via structures (46, 66). In one embodiment, the conductive materialportion 462 can include tungsten. Each conductive material portion 462can be a structure of integral construction, i.e., a single contiguousstructure. Each conductive material portion 462 can include a verticalconductive material portion and a horizontal conductive material portionthat do not have any interface there between, but can be divided onlygeometrically by a discontinuous change in the horizontalcross-sectional area of the conductive material portion as a function ofa vertical distance from the top surface of the alternating stack (32,46).

Each integrated line and via structure (46, 66) can include a contiguousmaterial portion that is contiguous throughout the entirety thereof anddoes not include any interface therein. Specifically, each of theplurality of integrated line and via structures (46, 66) can comprise anelectrically conductive electrode 46 and an electrically conductive viacontact 66 that adjoins, and overlies, the electrically conductiveelectrode 46 such that a contiguous material portion without aninterface therein contiguously extends through the electricallyconductive electrode 46 and the electrically conductive via contact 66.As used herein, an “interface” refers to any microscopic contiguoussurface at which different materials contact each other or a samematerial is spaced by a microscopic cavity or an impurity layer that isinherently present when one material is formed on another material inany environment that can introduce impurity materials. Because the samematerial is deposited simultaneously to form each contiguous materialportion of the electrically conductive via contact 66 and theelectrically conductive electrode within each integrated line and viastructure (46, 66), each contiguous material portion in an integratedline and via structure (46, 66) is free of any interface that dividesthe contiguous material portion into two portions.

In one embodiment, each conductive material portion 462 can be acontiguous material portion within a respective integrated line and viastructure (46, 66). In other words, each conductive material portion 462can be free of any interface therein and contiguously extend through theelectrically conductive electrode 46 and the electrically conductive viacontact 66 within a respective integrated line and via structure (46,66). If a metallic liner 461 is present within a line and via structure(46, 66), the metallic liner 461 can be a contiguous material portionthat is free of any interface therein and contiguously extends throughthe electrically conductive electrode 46 and the electrically conductivevia contact 66 within the integrated line and via structure (46, 66).Each conductive material portion 462 within an integrated line and viastructure (46, 66) can contiguously extend at least from a horizontalplane including the topmost surface of the alternating stack (32, 46) toa sidewall of the conductive material portion 462 located underneathanother horizontal plane including a top surface of the electricallyconductive electrode 46 within the integrated line and via structure(46, 66).

In one embodiment, each of the plurality of integrated line and viastructures (46, 66) can have a topmost surface that is coplanar with thetop surface of the alternating stack (32, 46), and electricallyconductive electrodes 46 within the plurality of integrated line and viastructures (32, 46) can be located at different levels within thealternating stack (32, 46). The different levels are vertically spacedby at least one insulator layer 32. In one embodiment, a dielectricliner 46 can laterally surround each electrically conductive via contact66 within the plurality of integrated line and via structures (46, 66).Each of the plurality of integrated line and via structures (46, 66) canbe electrically isolated from one another by the insulator layers 32 andthe dielectric liners 64.

Referring to FIG. 15, an insulating spacer 74 can be formed on thesidewalls of the backside contact trench 79 (See FIG. 11) by depositionof a contiguous dielectric material layer and an anisotropic etch. Theinsulating spacer 74 includes a dielectric material that can be the sameas, or different from, the dielectric material of the insulating liners64. For example, the insulating spacer 74 can include silicon oxide,silicon nitride, a dielectric metal oxide, a dielectric metaloxynitride, or a combination thereof. The thickness of the insulatingspacer 74, as measured at a bottom portion thereof, can be in a rangefrom 1 nm to 50 nm, although lesser and greater thicknesses can also beemployed. In one embodiment, the thickness of the insulating spacer 74can be in a range from 3 nm to 10 nm.

The backside contact trench 79 can be subsequently filled with a filllayer of another conductive material, which is herein referred to as asecond conductive material. The second conductive material can be thesame as, or can be different from, the first conductive material, i.e.,the conductive material of the integrated line and via structures (46,66). The second conductive material can be an electrically conductingmaterial, and can include a metal such as tungsten and/or a metalnitride. The deposited second conductive material can be planarizedemploying the mask layer 36 as a stopping layer for the planarizationprocess. Specifically, the portion of the conductive material formedover a horizontal plane including the top surface of the mask layer 36can be removed, for example, by chemical mechanical planarization, arecess etch, or a combination of a recess etch and chemical mechanicalplanarization. Remaining portions of the second conductive materialafter the planarization process constitutes a backside contact 76, whichcan provide a vertically conductive electrical path to an electricalnode of a device component within, or on, the substrate 8 and underneaththe alternating stack (32, 46). The backside contact 76 can be a sourceline electrically connected to a source region in the substrate 8. Thetop surface of the backside contact 76 can be coplanar with the topsurface of the mask layer 36.

In one embodiment, each electrically conductive electrode 46 among theplurality of line and via structures (46, 66) can comprise a word linethat function as a common control gate electrode for the plurality ofstacked memory devices including the channel and memory structures 55.In one embodiment, at least one of the plurality of contact opening 69(e.g., a first contact opening 69A) can have a first periphery containedentirety within a sidewall of one of the sacrificial layers 42 (e.g.,the N-th-from-top sacrificial layer 42F) and a second peripherycontained entirely within a sidewall of another of the sacrificiallayers 42 (e.g., the (N−1)-th-from-top sacrificial layer 42E). In oneembodiment, at least one of the plurality of contact opening 69 (e.g., afirst contact opening 69A) can have a first periphery contained entiretywithin a sidewall of one of the insulator layers 32 (e.g., the(N−1)-th-from-top insulator layer 32E) and a second periphery containedentirely within a sidewall of another of the insulator layer 32 (e.g.,the (N−2)-th-from-top sacrificial layer 42D).

The first exemplary structure of FIG. 15 includes a memory device, whichcomprises at least one memory cell (12, 55, 63) located on a substrate8. Each of the at least one memory cell contains a semiconductor channel60 including a vertical portion extending substantially perpendicular toa top surface of the substrate 8 and further includes a memory film 50contacting an outer sidewall of the semiconductor channel 60. The memorydevice further comprises an alternating stack (32, 46) of insulatorlayers 32 and electrically conductive electrodes 46 that laterallysurrounds portions of the at least one memory cell (12, 55, 63). Thememory device further comprises a plurality of integrated line and viastructures (46, 66) embedded within the insulator layers 32. Each of theplurality of integrated line and via structures (32, 46) comprises arespective one of the electrically conductive electrodes 46 and anelectrically conductive via contact 66 that adjoins, and overlies, therespective electrically conductive electrode 46 such that a conductivematerial portion 462 without an interface therein contiguously extendsthrough the respective electrically conductive electrode 46 and theelectrically conductive via contact 66. Each instance of theelectrically conductive electrodes 46 is a portion of a respective oneof the plurality of integrated line and via structures (46, 66).

In one embodiment, each instance of the electrically conductiveelectrodes 46 can include a control gate electrode for the at least onememory cell (12, 55, 63). The memory device can further include a sourceregion 12 located within, or on, the substrate 8 and contacting a bottomsurface of the at least one semiconductor channel 60. The memory devicecan further include a drain region 63 located on a top surface of one ofthe at least one semiconductor channel 60.

The memory device can include a dielectric liner 64 (e.g., thedielectric liner 64 in contact with a first electrically conductive viacontact 66A) having an outer sidewall and an inner sidewall. The outersidewall can contact a first electrically conductive electrode (e.g.,the (N−2)-th-from-top electrically conductive electrode 46D) within afirst integrated line and via structure (66A, 46F) (e.g., the integratedline and via structure including a third electrically conductive viacontact 66C and the (N−2)-th-from-top electrically conductive electrode46D), and a second electrically conductive electrode (e.g., the(N−1)-th-from-top electrically conductive electrode 46E) within a secondintegrated line and via structure (66B, 46E) (e.g., the integrated lineand via structure including a second electrically conductive via contact66B and the (N−1)-th-from-top electrically conductive electrode 46E).The second line structure (e.g., the (N−1)-th-from-top electricallyconductive electrode 46E) underlies the first line structure (e.g., the(N−2)-th-from-top electrically conductive electrode 46D). The innersidewall can contact an electrically conductive via contact (e.g., afirst electrically conductive via contact 66A) within a third integratedline and via structure (66C, 46D) (e.g., the integrated line and viastructure including the first electrically conductive via contact 66Aand the N-th-from-top electrically conductive electrode 46F) thatcontains a third line structure (e.g., the N-th-from-top electricallyconductive electrode 46F) underlying the second line structure (e.g.,the (N−1)-th-from-top electrically conductive electrode 46E). recesses41

Referring to FIG. 16, a second exemplary structure according to a secondembodiment of the present disclosure can be derived from the firstexemplary structure of FIG. 7 by omitting the processing steps of FIG. 8and by performing the processing steps of FIG. 9 to form a contiguousinsulating material layer 64L.

Referring to FIG. 17, the processing steps of FIG. 9 are performed toform insulating liners 64 on the sidewalls of the plurality of contactopenings 69. The insulating liners 64 can be formed on each sidewall ofthe plurality of contact openings 69 by performing an anisotropic etchof the contiguous insulating material layer 64L. Specifically, uponanisotropically etching the contiguous insulating material layer 64L,each remaining portion of the contiguous insulating material layer 74Lconstitutes an insulating liner 64. A portion of a top surface of asacrificial layer 42 is physically exposed at the bottom of each of theplurality of contact openings 69. Each insulating liner 64 can betopologically homeomorphic to a torus.

Referring to FIG. 18, a contiguous material layer 65 is formed bydeposition of a disposable material. The contiguous material layer 65 isa non-conformal layer formed non-conformal deposition of the dielectricmaterial. As used herein, a “non-conformal deposition” or an“anisotropic deposition” refers to a deposition process in which amaterial is non-conformally deposited, i.e., with different thicknessesat different locations. As used herein, a “disposable material” refersto a material that is temporarily present and is removed in a subsequentprocessing step. The disposable material is different from the secondmaterial, i.e., the material of the sacrificial layers 42.

In one embodiment, the disposable material can be a dielectric materialsuch as a doped silicate glass, an undoped silicate glass, anorganosilicate glass (which is also referred to as a SiCOH dielectricmaterial), amorphous carbon, diamond-like carbon (DLC), or a combinationthereof. In another embodiment, the disposable material can be asemiconductor material such as an elemental semiconductor material, analloy of at least two elemental semiconductor materials, a compoundsemiconductor material, an organic semiconductor material, or acombination thereof. For example, the disposable material can includeamorphous silicon or polycrystalline silicon. The non-conformaldeposition process can be, for example, plasma enhanced chemical vapordeposition (PECVD), physical vapor deposition (PVD), molecular beamdeposition, cluster beam ion implantation, or any other depositionmethod that can provide a directional impingement of molecules orclusters of a deposited material along the direction substantiallynormal to the top surface of the substrate 8.

The disposable material is deposited into, and over, the plurality ofcontact openings 69 (See FIG. 22) and over the mask layer 36 with suchan angular distribution in the direction of impingement of the depositedmolecules or material clusters that induces formation of a plurality ofencapsulated unfilled cavities 67, which are herein referred to “airgaps” or “contact opening air gaps.” As used herein, an “encapsulatedcavity” refers to a volume defined by a set of surfaces of at least onecondensed phase material such that the set of surfaces collectivelyconstitutes a closed surface in a three-dimensional space. As usedherein, an “encapsulated unfilled cavity” refers to an encapsulatedcavity devoid of any condensed phase material. As used herein, a“condensed phase material” refers to any of a solid material and aliquid material. As used herein, a “closed surface” refers to a surfacethat does not have any hole therein. In one embodiment, eachencapsulated unfilled cavity 67 can be topologically homeomorphic to asphere. In general, the less the angular spread in the distribution inthe direction of impingement of the deposited molecules or materialclusters, the lower the step coverage (the ability of the depositedmaterial to fill voids having a high aspect ratio) of the depositedmaterial, and the greater the size of the encapsulated unfilled cavities67 formed by the deposition of the deposited material. It is understoodthat “air gaps” of the present disclosure may include air or an inertgas, or may contain vacuum.

The disposable material of the contiguous material layer 65 can bedeposited non-conformally on the surfaces of the insulating liners 64.The plurality of encapsulated unfilled cavities 67 include volumes ofthe plurality of contact openings 69 that are not filled with thenon-conformally deposited material. The plurality of encapsulatedunfilled cavities 67 can additionally include volumes above the topsurface of the mask layer 36 and underneath bottom surfaces of thehorizontally extending portion of the contiguous material layer 65,which is located above the horizontal plane including the top surface ofthe mask layer 36. Due to the variations in the depths of the contactopenings 69, the vertical dimension (as measured from the bottommostportion to the topmost portion) of each encapsulated unfilled cavity 67can be different. For example, at least one first encapsulated unfilledcavity 67A including a volume of a first contact opening 69A (See FIG.22) can have a first vertical dimension, and at least one secondencapsulated unfilled cavity 67B including a volume of a second contactopening 69B (See FIG. 22) can have a second vertical dimension that isless than the first vertical dimension. In one embodiment, a pair of ani-th encapsulated unfilled cavity (67A, 67B, 67C, 67D, 67E, or 67F)including a volume of an i-th contact opening (69A, 69B, 69C, 69D, 69E,or 69F) and a j-th encapsulated unfilled cavity (67A, 67B, 67C, 67D,67E, or 67F) including a volume of a j-th contact opening (69A, 69B,69C, 69D, 69E, or 69F), for which each of the positive integers i and jdoes not exceed N and is different from each other, can have differentvertical dimensions. In one embodiment, the plurality of encapsulatedunfilled cavities 67 can include a set of encapsulated unfilled cavities67 that extend vertically over a different number of the sacrificiallayers 42 and/or over a different number of the insulator layers 32.

Each encapsulated unfilled cavity 67 is formed underneath thehorizontally extending portion of the contiguous material layer 65including the non-conformally deposited material. The portions of thecontiguous material layer 65 located below the horizontal planeincluding the top surface of the mask layer 36 and extending intovolumes of the contact openings 69 constitute encapsulating linerportions. Surfaces of the encapsulating liner portions constitutesurfaces of the plurality of encapsulated unfilled cavities 67.

After the processing steps of FIG. 18, an in-process device structure isformed. As used herein, an “in-process” device structure refers to atransitory device structure that is formed at one step during a seriesof processing sequences, and can be subsequently altered uponperformance of additional processing steps in the series of processingsteps. The in-process device structure includes a stack (32, 42)including an alternating plurality of material layers (e.g., thesacrificial layers 42) and insulator layers 32 and located over a topsurface of a substrate 8. The in-process device structure furtherincludes a plurality of contact openings 69 (See FIG. 22) located withinthe stack (32, 42). Each of the plurality of contact openings 69 extendsat least from a topmost surface of the alternating stack (32, 42) to asurface of a respective material layer (i.e., the various sacrificiallayers 42) among the material layers. The respective material layers arelocated at different levels. The in-process device structure furtherincludes a contiguous material layer 65 overlying the stack (32, 42). Aplurality of encapsulated unfilled cavities 67 is present underneathsurfaces of the contiguous material layer 65 that extend downward fromabove a horizontal plane including the top surface of the stack (32, 42)into the plurality of contact openings 69. Each of the plurality ofencapsulated unfilled cavities 67 occupies a portion of a volume of arespective one of the plurality of contact openings 69.

In one embodiment, the alternating plurality of material layers caninclude the sacrificial layers 42, which can include a dielectricmaterial such as silicon nitride. A bottom surface of each portion ofthe contiguous material layer 65 in the plurality of contact openingscan be in contact with a respective sacrificial layer 42.

At least one in-process memory cell (12, 55, 63) can be located on thesubstrate 8. Each of the at least one in-process memory cell (12, 55,63) can include a semiconductor channel 60 including a vertical portionextending substantially perpendicular to a top surface of the substrate8, and a memory film 50 contacting an outer sidewall of thesemiconductor channel 60. In one embodiment, at least one of theplurality of contact opening 69 (e.g., a first contact opening 69A) canhave a first periphery contained entirety within a sidewall of one ofthe sacrificial layers 42 (e.g., the N-th-from-top sacrificial layer42F) and a second periphery contained entirely within a sidewall ofanother of the sacrificial layers 42 (e.g., the (N−1)-th-from-topsacrificial layer 42E). In one embodiment, at least one of the pluralityof contact opening 69 (e.g., a first contact opening 69A) can have afirst periphery contained entirety within a sidewall of one of theinsulator layers 32 (e.g., the (N−1)-th-from-top insulator layer 32E)and a second periphery contained entirely within a sidewall of anotherof the insulator layer 32 (e.g., the (N−2)-th-from-top sacrificial layer42D).

Referring to FIG. 19, a photoresist layer 77 can be applied over thestack of the mask layer 36 and the contiguous material layer 65, andlithographically patterned to form at least one opening in an area inwhich formation of a backside contact 76 (See FIG. 32) is desired. Thepattern in the photoresist layer 77 can be transferred through thecontiguous material layer 65, the mask layer 36, and the alternatingstack (32, 42) employing an anisotropic etch to form a via trench thatextends at least to the top surface of the substrate 8. The via trenchthat extends at least to the top surface of the substrate 8 is a contactopening, and is herein referred to as a backside contact trench 79. Inone embodiment, the surface that is physically exposed at the bottom ofthe backside contact trench 79 can be implanted with electrical dopants,such as p-type dopants or n-type dopants, to form a source region 12 forvertical memory devices including the channel and memory structures 55.The photoresist layer 77 can be subsequently removed, for example, byashing. Sidewalls of the sacrificial layers 42 and sidewalls of theinsulator layers 32 are physically exposed as surfaces of the backsidecontact trench 79.

Referring to FIG. 20, the processing steps of FIG. 12 are performed toform a plurality of recesses 41. The sacrificial layers 42 (See FIG. 19)can be removed selective to the insulator layers 32 to form a pluralityof recesses 41 while the plurality of encapsulated unfilled cavities 67is present. The backside contact trench 79 can be employed as a conduitthat introduces etchants for removing the second material of thesacrificial layers 42 during the selective etch process that forms theplurality of recesses 41. In this case, the removal of the etchedportions of the sacrificial layers 42 selective to the insulator layers32 can be performed by introducing an etchant to the sacrificial layers42 through the backside contact trench 79. The insulating liners 64protect the sidewalls of each of the plurality of contact openings 69from an etchant used to remove at least a portion of each sacrificiallayer 42.

The plurality of recesses 41 can extend substantially parallel to thetop surface of the substrate 8. Because a bottom portion of thecontiguous material layer 65 is present at the bottom of each contactopening 69, a surface of each of the plurality of recesses 41 can be abottom surface of a respective portion of the non-conformally depositedmaterial, i.e., a respective portion of the contiguous material layer65.

Referring to FIG. 21, the processing steps of FIG. 13 can besubsequently performed to simultaneously deposit a conductive materialin the plurality of recesses 41 and the backside contact trench 79, andover the top surface of the contiguous material layer 65. The conductivematerial is herein referred to as a first conductive material, or anelectrically conductive electrode material. The first conductivematerial can be deposited employing the same type of processing steps asin the processing steps of FIG. 18. The backside contact trench 79 canbe employed as a conduit that introduces the first conductive materialinto the plurality of recesses 41. In this case, the deposition of thefirst conductive material into the plurality of recesses 41 can beperformed by introducing of the deposited conductive material into theplurality of recesses 41 through the backside contact trench 79. Theinsulating liners 64 and contiguous material layer 65 (which is anon-conformal layer) substantially prevent the electrically conductiveelectrode material from covering (i.e., contacting) the sidewalls ofeach contact opening 69.

Simultaneous deposition of the conductive material in the plurality ofrecesses 41, on the sidewalls and the bottom surface of the backsidecontact trench 79 (See FIG. 17), and over the top surface of thecontiguous material layer 65 forms a plurality of electricallyconductive electrodes 46 in the plurality of recesses 41 and acontiguous conductive material layer 72L. Each electrically conductiveelectrode 46 can be a conductive line structure. The contiguousconductive material layer 72L includes a portion formed on the sidewallsof the bottom surface of the backside contact trench 79, and a portionoverlying the top surface of the mask layer 36. The contiguousconductive material layer 72L and the plurality of electricallyconductive electrodes 46 are formed as an integral structure, i.e., asingle contiguous structure.

After the processing steps of FIG. 21, an in-process device structure isformed. The in-process device structure includes a stack (32, 46)including an alternating plurality of material layers (e.g., theelectrically conductive electrodes 46) and insulator layers 32 andlocated over a top surface of a substrate 8. The in-process devicestructure further includes a plurality of contact openings 69 (See FIG.22) located within the stack (32, 46). Each of the plurality of contactopenings 69 extends at least from a topmost surface of the alternatingstack (32, 46) to a surface of a respective material layer (i.e., thevarious electrically conductive electrodes 46) among the materiallayers. The respective material layers are located at different levels.The in-process device structure further includes a contiguous materiallayer 65 overlying the stack (32, 46). A plurality of encapsulatedunfilled cavities 67 is present underneath surfaces of the contiguousmaterial layer 65 that extend downward from above a horizontal planeincluding the top surface of the stack (32, 46) into the plurality ofcontact openings 69. Each of the plurality of encapsulated unfilledcavities 67 occupies a portion of a volume of a respective one of theplurality of contact openings 69.

In one embodiment, the alternating plurality of material layers caninclude the electrically conductive electrodes 46, which can include aconductive material such as tungsten. A bottom surface of each portionof the contiguous material layer 65 in the plurality of contact openingscan be in contact with a respective electrically conductive electrode46.

Referring to FIG. 22, the deposited conductive material is etched back,for example, by an isotropic etch. The processing steps of FIG. 14 canbe employed. The conductive material layer 72L can be removed by theetch-back process. Remaining contiguous portion of the depositedconductive material include a plurality of integrated line and viastructures (46, 66).

Referring to FIG. 23, the contiguous material layer 65 can be removedfrom above the top surface of the mask layer 36 and from inside theplurality of contact openings 69 without forming a hole in theinsulating liners 64. In one embodiment, the contiguous material layer65 can include a material that is different from the material of theinsulating liners 64. In this case, the contiguous material layer 65 canbe removed selective to the material of the insulating liners 64. Inanother embodiment, the contiguous material layer 65 can include thesame material as the insulating liners 64. In this case, thehorizontally extending portion of the contiguous material layer 65 abovethe top surface of the mask layer 36 can be removed, for example, by arecess etch and/or chemical mechanical planarization, and each bottomportion of the contiguous material layer 65 in contact with a topsurface of an electrically conductive electrodes 46 can be removed by ananisotropic etch to physically expose a top surface of an underlyingelectrically conductive electrode 46 within each contact opening 69.

Referring to FIG. 24, the processing steps of FIG. 8 can be performed toform peripheral contact openings 89.

Referring to FIG. 25, insulating spacers 74 can be formed on thesidewalls of the backside contact trench 79, the plurality of contactvia trenches 69, and the peripheral contact openings 89. The insulatingspacers 74 can be formed by deposition of a contiguous dielectricmaterial layer and an anisotropic etch. The insulating spacers 74includes a dielectric material that can be the same as, or differentfrom, the dielectric material of the insulating liners 64. For example,the insulating spacers 74 can include silicon oxide, silicon nitride, adielectric metal oxide, a dielectric metal oxynitride, or a combinationthereof. The thickness of the insulating spacers 74, as measured at abottom portion thereof, can be in a range from 1 nm to 50 nm, althoughlesser and greater thicknesses can also be employed. In one embodiment,the thickness of the insulating spacer 74 can be in a range from 3 nm to10 nm.

Referring to FIG. 26, the backside contact trench 79, the plurality ofcontact via trenches 69, and the peripheral contact openings 89 can besubsequently filled with a fill layer of another conductive material,which is herein referred to as a second conductive material. The secondconductive material can be the same as, or can be different from, thefirst conductive material, i.e., the conductive material of theintegrated line and via structures (46, 66). The second conductivematerial can be an electrically conducting material, and can include ametal such as tungsten and/or a metal nitride. The deposited secondconductive material can be planarized employing the mask layer 36 as astopping layer for the planarization process. Specifically, the portionof the conductive material formed over a horizontal plane including thetop surface of the mask layer 36 can be removed, for example, bychemical mechanical planarization, a recess etch, or a combination of arecess etch and chemical mechanical planarization. Remaining portions ofthe second conductive material after the planarization processconstitutes a plurality of electrically conductive via contacts 66, abackside contact 76, and peripheral device electrically conductive viacontacts 86. The backside contact 76 can be a source line electricallyconnected to a source region in the substrate 8.

In one embodiment, each electrically conductive electrode 46 among theplurality of line and via structures (46, 66) can comprise a word linethat function as a common control gate electrode for the plurality ofstacked memory devices including the channel and memory structures 55.In one embodiment, at least one of the plurality of contact opening 69(e.g., a first contact opening 69A) can have a first periphery containedentirety within a sidewall of one of the sacrificial layers 42 (e.g.,the N-th-from-top sacrificial layer 42F) and a second peripherycontained entirely within a sidewall of another of the sacrificiallayers 42 (e.g., the (N−1)-th-from-top sacrificial layer 42E). In oneembodiment, at least one of the plurality of contact opening 69 (e.g., afirst contact opening 69A) can have a first periphery contained entiretywithin a sidewall of one of the insulator layers 32 (e.g., the(N−1)-th-from-top insulator layer 32E) and a second periphery containedentirely within a sidewall of another of the insulator layer 32 (e.g.,the (N−2)-th-from-top sacrificial layer 42D).

The exemplary device of the present disclosure can include a verticalNAND device containing a plurality of semiconductor channels 60. Atleast one end portion of each of the plurality of semiconductor channels60 extends substantially perpendicular to the major surface of thesubstrate 8. The vertical NAND device further contains a plurality ofcharge storage regions. Each charge storage region located in a memoryfilm 50 and adjacent to a respective one of the plurality ofsemiconductor channels 60. The vertical NAND device contains a pluralityof control gate electrodes, embodied as the electrically conductiveelectrodes 46, that extend substantially parallel to the major surfaceof the substrate 8. The plurality of control gate electrodes comprise atleast a first control gate electrode (e.g., the first-from-topelectrically conductive electrode 46A) located in the first device leveland a second control gate electrode (e.g., the second-from-topelectrically conductive electrode 46B) located in the second devicelevel below the first device level. The first control gate electrode cancomprises an end portion of a first word line of the plurality of wordlines, and the second control gate electrode can comprise an end portionof a second word line of the plurality of word lines. The first and thesecond word lines extend from the device region 100 to the contactregion 300. In one embodiment, the plurality of word lines can comprisetungsten or titanium nitride and tungsten word lines deposited bychemical vapor deposition.

In one embodiment, a source line 76 extends through a dielectricinsulated trench in the stack to electrically contact the semiconductorchannels 60. A bit line (not shown) can be electrically connected to thedrain regions 63 via at least one contact via structures (not shown). Asource select gate electrode (not shown) may be located adjacent to thesemiconductor channels 60 between the major surface of the substrate 8and the plurality of control gate electrodes embodied as theelectrically conductive electrodes 46. A drain select gate electrode(not shown) can be located adjacent to the semiconductor channels 60above the plurality of control gate electrodes.

In the various embodiments of the present disclosure, a total of twophotolithography steps can be used during the steps of forming the masklayer 36 with the plurality of openings, forming the plurality ofcontact openings 69, selectively removing the sacrificial layers 42, anddepositing the plurality of electrically conductive via contacts 46 andthe plurality of electrically conductive electrodes 66. Specifically, afirst lithography step is employed to pattern the mask layer 36 at aprocessing step of FIG. 2, and the second lithography step is employedto initially pattern the slimming layer prior to etching the topmostinsulator layer 32 at a processing step of FIG. 4. The peripheralcontact openings 89 (See, e.g., FIG. 8) can be formed employing only onephotolithographic process.

Unlike the prior art methods, sacrificial layers 42 need not be in astep pattern in the contact region. Thus, in some embodiments of thepresent disclosure, the sacrificial layers 42 are not in a step patternin the contact region, and laterally contact the same sidewall of adielectric support pillar 38.

In one embodiment, chemical mechanical polishing is not used during thesteps of forming the mask layer 36 with the plurality of openings,forming the plurality of contact openings 69, selectively removing thesacrificial layers 32, and depositing the plurality of electricallyconductive via contacts 66 and the plurality of electrically conductiveelectrodes 46. In one embodiment, unlike the prior art methods, aninsulating support pillar is not formed through the stack prior to thestep of selectively removing the sacrificial layers 42.

According to an aspect of the present disclosure, a method of makingmulti-level contacts is provided. An in-process multilevel device isprovided, which comprises a device region and a contact region includinga stack of plurality of alternating sacrificial layers and insulatinglayers located over a major surface of a substrate. A plurality ofcontact openings is formed, each of which extends substantiallyperpendicular to the major surface of the substrate to the plurality ofsacrificial layers. Each of the plurality of contact openings extendsthrough the stack to a respective one of the sacrificial layers. Thesacrificial layer are selectively removed from the stack to form aplurality of recesses extending substantially parallel to the majorsurface of the substrate between the insulating layers. A plurality ofelectrically conductive via contacts is deposited in the plurality ofthe contact openings and a plurality of electrically conductiveelectrodes in the plurality of recesses in one deposition step.

According to an aspect of the present disclosure, a method of forming apatterned structure is provided. A stack is formed over a top surface ofa substrate. The stack includes an alternating plurality of insulatorlayers and sacrificial layers. A plurality of contact openings is formedwithin the stack. Each of the plurality of contact openings extends froma topmost surface of the stack to a surface of a respective materiallayer. The respective material layers include sacrificial layers locatedat different levels or insulator layers located at different levels. Aplurality of recesses is formed by removing the sacrificial layersselective to the insulator layers. The plurality of recesses extendssubstantially parallel to the top surface of the substrate. A conductivematerial is simultaneously deposited in the plurality of contactopenings and the plurality of recesses. A plurality of electricallyconductive via contacts is formed the plurality of the contact openingsand a plurality of electrically conductive electrodes is formed in theplurality of recesses.

According to another aspect of the present disclosure, another method offorming a patterned structure is provided. A stack is formed over a topsurface of a substrate. The stack includes an alternating plurality ofinsulator layers and sacrificial layers. A mask layer with a pluralityof openings is formed over the stack. A layer of a slimming material isformed over the mask layer. Etch processes and trimming processes arealternately performed. Portions of the stack located underneath openingsthat are not covered by the slimming material are etched in each of theetch processes. A total number of openings not covered by the slimmingmaterial increases in each of the trimming processes by partial removalof the slimming material. A plurality of contact openings is formedwithin the stack by the alternately performed etch processes andtrimming processes. Each of the plurality of contact openings extendsfrom a topmost surface of the stack to a surface of a respectivematerial layer. The respective material layers includes sacrificiallayers located at different levels or insulator layers located atdifferent levels.

According to yet another aspect of the present disclosure, a memorydevice is provided, which includes at least one memory cell located on asubstrate. Each of the at least one memory cell contains a semiconductorchannel including a vertical portion extending substantiallyperpendicular to a top surface of the substrate and further including amemory film contacting an outer sidewall of the semiconductor channel.The memory device further includes an alternating stack of insulatorlayers and electrically conductive electrodes that laterally surroundsportions of the at least one memory cell. The memory device furtherincludes a plurality of integrated line and via structures embeddedwithin the insulator layers. Each of the plurality of integrated lineand via structures comprises a respective one of the electricallyconductive electrodes and an electrically conductive via contact thatadjoins, and overlies, the respective electrically conductive electrodesuch that a conductive material portion without an interface thereincontiguously extends through the respective electrically conductiveelectrode and the electrically conductive via contact. Each instance ofthe electrically conductive electrodes is a portion of a respective oneof the plurality of integrated line and via structures.

According to even another embodiment of the present disclosure, a methodof forming a patterned structure is provided. A stack is formed over atop surface of a substrate. The stack includes an alternating pluralityof insulator layers and sacrificial layers. A plurality of contactopenings is formed within the stack. Each of the plurality of contactopenings extends from a topmost surface of the stack to a surface of arespective material layer. The respective material layers includesacrificial layers located at different levels or insulator layerslocated at different levels. A material is non-conformally depositedover the plurality of contact openings. A plurality of encapsulatedunfilled cavities is formed underneath a horizontally extending portionof a contiguous material layer including the non-conformally depositedmaterial. The plurality of encapsulated unfilled cavities includesvolumes of the plurality of contact openings that are not filled withthe non-conformally deposited material.

According to still another embodiment of the present disclosure, anin-process device structure is provided. The in-process device structurecomprises a stack including an alternating plurality of material layersand insulator layers and located over a top surface of a substrate. Thein-process device structure further includes a plurality of contactopenings located within the stack. Each of the plurality of contactopenings extends from a topmost surface of the stack to a surface of arespective material layer among the material layers. The respectivematerial layers are located at different levels. The in-process devicestructure further comprises a contiguous material layer overlying thestack and including encapsulating liner portions that extend downwardfrom above the topmost surface of the stack into the plurality ofcontact openings to define a plurality of encapsulated unfilledcavities. Each of the plurality of encapsulated unfilled cavities is ina volume defined by a contiguous surface of a respective one of theencapsulating liner portions.

Although the foregoing refers to particular preferred embodiments, itwill be understood that the disclosure is not so limited. It will occurto those of ordinary skill in the art that various modifications may bemade to the disclosed embodiments and that such modifications areintended to be within the scope of the disclosure. Where an embodimentemploying a particular structure and/or configuration is illustrated inthe present disclosure, it is understood that the present disclosure maybe practiced with any other compatible structures and/or configurationsthat are functionally equivalent provided that such substitutions arenot explicitly forbidden or otherwise known to be impossible to one ofordinary skill in the art. All of the publications, patent applicationsand patents cited herein are incorporated herein by reference in theirentirety.

What is claimed is:
 1. A method of forming contacts in a multilayermemory device, comprising: a) providing an in-process memory device,comprising: a contact region; a device region; a stack of alternatingplurality of sacrificial layers and insulating layers over a substrateand extending in a first direction substantially parallel to a majorsurface of the substrate from the contact region to the device region;and a hard mask layer formed over the contact region and the deviceregion; b) forming a plurality of contact openings in the contactregion, each contact opening extending in a second directionsubstantially perpendicular to the major surface of the substratethrough the hard mask layer and a portion of the stack to a respectivesacrificial layer; c) forming an insulating liner covering sidewalls ofeach contact opening of the plurality of contact openings, wherein theinsulating liner does not cover a bottom of each contact opening suchthat a portion of the respective sacrificial layer is exposed at thebottom of the contact opening; d) forming a non-conformal layer over thehard mask layer that covers a top opening of each contact opening toform a corresponding contact opening air gap.
 2. The method of claim 1,wherein step c) comprises: forming a conformal insulating material layercovering the sidewalls and bottom of each contact opening; selectivelyetching the conformal insulating material layer on the bottom of eachcontact opening to expose a portion of the respective sacrificial layer.3. The method of claim 1, wherein: the insulating liner comprisessilicon oxide; each insulating layer comprises silicon oxide; and eachsacrificial layer comprises silicon nitride.
 4. The method of claim 3,further comprising: e) forming a backside contact trench extending inthe second direction through the non-conformal layer, the hard masklayer, and the stack to the substrate; wherein the backside contacttrench exposes sidewall portions of each of the sacrificial layers inthe stack.
 5. The method of claim 4, further comprising: f) selectivelyremoving at least a portion of each sacrificial layer in the stackthrough the backside contact trench to form a plurality of recesses,wherein each recess extends along the first direction from the deviceregion to the contact region to connect to a respective one of theplurality of air gaps.
 6. The method of claim 5, wherein during step 0the insulating liner protects the sidewalls of each of the plurality ofcontact openings from an etchant used to remove the at least a portionof each sacrificial layer.
 7. The method of claim 6, further comprising:g) depositing an electrically conductive electrode material to: cover asurface of the non-conformal layer; fill each of the recesses throughthe backside contact trench; and conformally cover sidewalls and abottom of the backside contact trench, wherein the filled recesses forma plurality of electrically conductive electrodes extending in the firstdirection from the device region to the contact region.
 8. The method ofclaim 7, wherein, during step g) the insulating liner and non-conformallayer substantially prevent the electrically conductive electrodematerial from covering the sidewalls of each contact opening.
 9. Themethod of claim 8, wherein the electrically conductive electrodematerial comprises a metal or metal nitride.
 10. The method of claim 9,wherein electrically conductive electrode material comprises tungsten.11. The method of claim 8, further comprising: h) removing thenon-conformal layer to expose a surface of the hard mask layer andopenings to each of the contact openings in the hard mask layer.
 12. Themethod of claim 11, further comprising: i) forming an insulating spacersubstantially covering the sidewalls of each of the contact openings andsidewalls of the back contact trench while leaving the bottoms of eachof the contact openings and a bottom of the back contact trench exposed.13. The method of claim 12, further comprising: j) depositing a filllayer of electrically conducting material on the hard mask andsubstantially filling each of the contact openings and the back contacttrench.
 14. The method of claim 13, wherein the fill layer ofelectrically conducting material comprises a metal or metal nitride. 15.The method of claim 14, wherein the fill layer of electricallyconducting material comprises tungsten.
 16. The method of claim 13,further comprising: k) removing a portion of the fill layer ofelectrically conducting material covering the hard mask layer to exposea surface of the hard mask layer comprising the tops of the filledcontact openings and a top of the filed backside contact trench.
 17. Themethod of claim 16, wherein step k) results in: a plurality ofelectrically conductive via contacts, each via contact extending in thesecond direction from the exposed top of the filled contact opening to arespective one of the plurality of electrically conductive electrodes;and a backside contact extending in the second direction from theexposed top of the backside contact trench to the substrate; wherein:each one of the plurality of electrically conductive via contacts is inelectrical contact with a respective one of the electrically conductiveelectrodes and electrically insulated from the others of the pluralityof electrically conductive via contacts and the plurality ofelectrically conductive electrodes; and the backside contact is inelectrical contact with the substrate and electrically insulated fromthe plurality of electrically conductive via contact via contacts andthe plurality of electrically conductive electrodes.
 18. The method ofclaim 17, wherein: the in-process memory device further comprises aperipheral device region covered by the hard mask layer; prior to stepi) the method further comprises forming at least one peripheral contactopening extending in the second direction through the hard mask layer toa peripheral device in the peripheral device region; step i) comprisesforming the insulating spacer to substantially cover sidewalls of the atleast one peripheral device contact opening while exposing a bottomportion of the peripheral device contact opening that contacts orcomprises at least a portion of the peripheral device; and step j)comprises filling the peripheral device contact opening with theelectrically conducting material.
 19. The method of claim 18, wherein:step k) comprises exposing a surface of the hard mask layer comprising atop of the filled peripheral device contact opening which results in aperipheral device electrically conductive via contact extending from thetop of the peripheral device contact opening to the peripheral device.20. The method of claim 17, wherein: the device region comprises anarray of monolithic three dimensional NAND strings having a plurality ofdevice levels disposed above the substrate; the backside contactcomprises a source line of the array of monolithic three dimensionalNAND strings; electrically conductive electrodes comprise verticallyseparated word lines; and each word line electrically contacts arespective one of the plurality of electrically conductive via contacts;and each word line electrically contacts or comprises a respective oneof a plurality of vertically separated control gate electrodes of thearray of monolithic three dimensional NAND strings.
 21. The method ofclaim 20, wherein: the substrate comprises a silicon substrate; a drivercircuit associated with the array is located above or in the siliconsubstrate; the at least one peripheral device comprises transistordevice in the driver circuit; and the peripheral device via contact isin electrical contact with or comprises a gate of the transistor device.22. The method of claim 18, wherein forming the peripheral contactopening comprises only one photolithographic process.
 23. The method ofclaim 22, wherein the photolithographic process comprises: depositing aconformal photoresist layer on the hard mask layer and filling thecontact openings and backside contact trench; patterning the conformalphotoresist layer to expose a portion of the hard mask layer overlayingthe peripheral device; selectively etching through the exposed portionof the hard mask layer to form the peripheral contact opening; andremoving the conformal photoresist layer.
 24. The method of claim 1,wherein step b) comprises only one photolithographic process.
 25. Themethod of claim 4, wherein step e) comprises only one photolithographicprocess.
 26. An in-process memory device comprising: a contact region; adevice region; a stack of alternating plurality of sacrificial layersand recesses over a substrate and extending in a first directionsubstantially parallel to a major surface of the substrate from thecontact region to the device region; a hard mask layer located over thecontact region and the device region; a plurality of contact openings inthe contact region, each contact opening extending in a second directionsubstantially perpendicular to the major surface of the substratethrough the hard mask layer and a portion of the stack to a respectivesacrificial layer; an insulating liner covering sidewalls of eachcontact opening of the plurality of contact openings, wherein theinsulating liner does not cover a bottom of each contact opening suchthat a portion of the respective sacrificial layer is exposed at thebottom of the contact opening; and a non-conformal layer over the hardmask layer that covers a top opening of each contact opening to form acorresponding contact opening air gap, wherein each one of the pluralityof recesses contacts a respective contact opening air gap.
 27. Thedevice of claim 26, further comprising: a backside contact trenchextending in the second direction through the non-conformal layer, thehard mask layer, and the stack to the substrate; wherein each recess isexposed to the backside contact trench through a respective opening in asidewall of the backside contact trench.
 28. The device of claim 26,further comprises a peripheral device region comprising a peripheraldevice.
 29. The device of claim 26, wherein: the device region comprisesan array of monolithic three dimensional NAND strings having a pluralityof device levels disposed above the substrate; each recess defines aspace for receiving a respective word line of the array of monolithicthree dimensional NAND strings.
 30. The device of claim 26, wherein: theinsulating liner comprises silicon oxide, and each insulating layercomprises silicon oxide.